Paul,

I am unable to create a small example to reproduce the problem.  However, in
our enterprise application, I can uncomment the cached controls I Disposed,
and the exception reappears.  I'm reasonably convinced that Disposing of our
cached controls avoids the problem.  I can't explain why.

The error message that led me to my solution was "Cannot call Dispose while
doing CreateHandle()."  Using the .NET Reflector to look at the Control
class, I found this exception occurs only when Dispose(true) is called, and
only when the control believes it is currently being created.  The GC thread
must have called Dispose(true).  I'm not sure how.  CreateHandle() calls
SetState(262144, true) when it begins.  Dispose(true) checks for this flag
and, if set, throws an InvalidOperationException with the error message
above.  How can the same control be created and disposed at the same time?

I only saw this particular exception once.  I usually get some kind of null
pointer exception.  The pattern always looks something like the stack trace I
included at the bottom.

Here, a form is being instantiated.  The form's constructor constructs
MyControl.  The MyControl constructor starts the Windows form designer code.  
At the point of the exception, the form designer is setting a label's text.  
As you can see, changing the text triggers the label to measure its text.  
Measuring the text requires a Graphics object.  Creating a graphics object
requires a valid window handle, so the control creates itself.  Note that the
label has not yet been added to any parent.

(I find it odd that the Framework would create a control before it's even
been added to a parent, much less become visible.  A better solution to me
would be to measure the text in CreateControl.  This behavior may be related
to the crash.)

To create itself, the control calls CreateWindowEx.  CreateWindowEx fires
the WM_CREATE message back to the control, which its WndProc forwards to the
WmCreate() method.

WmCreate forwards the message to its DefWndProc.  Then, it immediately fires
the WM_CHANGEUISTATE message with a parameter of UIS_INITIALIZE (3).  Windows
bounces the message to a callback, which trickles it back up to some
control's WmUpdateUIState method.  WmUpdateUIState forwards it back to
DefWndProc, which sends it to the control's NativeWindow, where it crashes.  
I wish I could determine which windows got the messages, and what the state
was, but the debugger doesn't let me inspect managed variables when debugging
a native crash.

Looking at a decompiled version of NativeWindow.DefWndProc, it looks like
the control is trying to call the win32 DefWndProc function.  I'm not sure
why that crashes.  It may be a simple check for null would fix the problem.  
This is the decompiled version:

      public void DefWndProc(ref Message m)
      {
          if (this.previousWindow == null)
          {
              if (this.defWindowProc == IntPtr.Zero)
              {

                  return;
              }
              m.Result =
System.Windows.Forms.UnsafeNativeMethods.CallWindowProc(this.defWindowProc,
m.HWnd, m.Msg, m.WParam, m.LParam);
              return;
          }
          m.Result = this.previousWindow.Callback(m.HWnd, m.Msg, m.WParam,
m.LParam);
      }

If you look at the implementation of NativeWindow, you will see each
NativeWindow has a pointer to a previous window and a pointer to a next
window.  The .NET Framework maintains a doubly linked list of windows.  Every
NativeWindow has two variables, previousWindow and nextWindow, that point to
other NativeWindows.  I don't fully understand this list, but I think it
tracks window handles.  Creating a handle adds it and its window to the list,
and destroying one removes them.   Furthermore, NativeWindows forward
unhandled messages to their previous windows.  In this case, I don't think
there is a previous window.  Maybe that indicates the topmost window, or
maybe it's because a parent has not been created.  I'm not sure.

Our Window initialization takes a while.  It's possible the garbage
collector thread collected some forms while they were being initialized.  The
garbage collector thread would have to reclaim the window handles, because
they did not get properly Disposed.  If the NativeWindow list maintenance
were not synchonized, there might be a race condition between the UI thead
and the GC thread.  However, the Framework code looks safe, because it
synchronizes on the NativeWindow type.  If Dispose and CreateHandle ran at
the same time, they shouldn't corrupt each other.  It may be that a Dispose
in between CreateHandle calls somehow corrupted memory.

I think I have a solution, but I'm clueless as to why it works.  What would
really help: if someone at Microsoft would analyze a dump.  I can produce
them on demand.

(Is there a way to generate a dump from inside Visual Studio?  I can do so
from windbg.exe, but that tool doesn't show me the managed methods, so I
can't tell if it's the same stack trace.)

BEGIN Typical Stack Trace  
=====================================================

 00000000()
 
system.windows.forms.dll!System.Windows.Forms.NativeWindow.DefWndProc(System.Windows.Forms.Message m) + 0xde bytes
 
system.windows.forms.dll!System.Windows.Forms.Control.DefWndProc(System.Windows.Forms.Message m) + 0xb bytes
 
system.windows.forms.dll!System.Windows.Forms.Control.WmUpdateUIState(System.Windows.Forms.Message m) + 0x3b bytes
 
system.windows.forms.dll!System.Windows.Forms.Control.WndProc(System.Windows.Forms.Message m) + 0x718 bytes
 
system.windows.forms.dll!System.Windows.Forms.GroupBox.WndProc(System.Windows.Forms.Message m) + 0x45 bytes
 
system.windows.forms.dll!ControlNativeWindow.OnMessage(System.Windows.Forms.Message m) + 0xb bytes
 
system.windows.forms.dll!ControlNativeWindow.WndProc(System.Windows.Forms.Message m) + 0xbc bytes
 system.windows.forms.dll!System.Windows.Forms.NativeWindow.Callback(int
hWnd, int msg, int wparam, int lparam) + 0x30 bytes
 
system.windows.forms.dll!System.Windows.Forms.NativeWindow.DefWndProc(System.Windows.Forms.Message m) + 0xde bytes
 
system.windows.forms.dll!System.Windows.Forms.Control.DefWndProc(System.Windows.Forms.Message m) + 0xb bytes
 
system.windows.forms.dll!System.Windows.Forms.Control.WmUpdateUIState(System.Windows.Forms.Message m) + 0x3b bytes
 
system.windows.forms.dll!System.Windows.Forms.Control.WndProc(System.Windows.Forms.Message m) + 0x718 bytes
 
system.windows.forms.dll!System.Windows.Forms.ScrollableControl.WndProc(System.Windows.Forms.Message m) + 0x36 bytes
 
system.windows.forms.dll!System.Windows.Forms.ContainerControl.WndProc(System.Windows.Forms.Message m) + 0x17 bytes
 
system.windows.forms.dll!System.Windows.Forms.Application.ParkingWindow.WndProc(System.Windows.Forms.Message m) + 0xe bytes
 
system.windows.forms.dll!ControlNativeWindow.OnMessage(System.Windows.Forms.Message m) + 0xb bytes
 
system.windows.forms.dll!ControlNativeWindow.WndProc(System.Windows.Forms.Message m) + 0xbc bytes
 system.windows.forms.dll!System.Windows.Forms.NativeWindow.Callback(int
hWnd, int msg, int wparam, int lparam) + 0x30 bytes
 
system.windows.forms.dll!System.Windows.Forms.NativeWindow.DefWndProc(System.Windows.Forms.Message m) + 0xde bytes
 
system.windows.forms.dll!System.Windows.Forms.Control.DefWndProc(System.Windows.Forms.Message m) + 0xb bytes
 
system.windows.forms.dll!System.Windows.Forms.Control.WndProc(System.Windows.Forms.Message m) + 0x960 bytes
 
system.windows.forms.dll!System.Windows.Forms.ScrollableControl.WndProc(System.Windows.Forms.Message m) + 0x36 bytes
 
system.windows.forms.dll!System.Windows.Forms.ContainerControl.WndProc(System.Windows.Forms.Message m) + 0x17 bytes
 
system.windows.forms.dll!System.Windows.Forms.Application.ParkingWindow.WndProc(System.Windows.Forms.Message m) + 0xe bytes
 
system.windows.forms.dll!ControlNativeWindow.OnMessage(System.Windows.Forms.Message m) + 0xb bytes
 
system.windows.forms.dll!ControlNativeWindow.WndProc(System.Windows.Forms.Message m) + 0xbc bytes
 system.windows.forms.dll!System.Windows.Forms.NativeWindow.Callback(int
hWnd, int msg, int wparam, int lparam) + 0x30 bytes
 
system.windows.forms.dll!System.Windows.Forms.NativeWindow.DefWndProc(System.Windows.Forms.Message m) + 0xde bytes
 
system.windows.forms.dll!System.Windows.Forms.Control.DefWndProc(System.Windows.Forms.Message m) + 0xb bytes
 
system.windows.forms.dll!System.Windows.Forms.Control.WndProc(System.Windows.Forms.Message m) + 0x960 bytes
 
system.windows.forms.dll!System.Windows.Forms.Label.WndProc(System.Windows.Forms.Message m) + 0xca bytes
 
system.windows.forms.dll!ControlNativeWindow.OnMessage(System.Windows.Forms.Message m) + 0xb bytes
 
system.windows.forms.dll!ControlNativeWindow.WndProc(System.Windows.Forms.Message m) + 0xbc bytes
 system.windows.forms.dll!System.Windows.Forms.NativeWindow.Callback(int
hWnd, int msg, int wparam, int lparam) + 0x30 bytes
 008d8f32()
 user32.dll!GetDC()  + 0x72
 user32.dll!GetDC()  + 0x154
 user32.dll!GetParent()  + 0x16c
 user32.dll!SendMessageW()  + 0x49
 system.windows.forms.dll!System.Windows.Forms.Control.SendMessage(int msg,
int wparam, int lparam) + 0x42 bytes
 
system.windows.forms.dll!System.Windows.Forms.Control.WmCreate(System.Windows.Forms.Message m) + 0x45 bytes
 
system.windows.forms.dll!System.Windows.Forms.Control.WndProc(System.Windows.Forms.Message m) + 0x387 bytes
 
system.windows.forms.dll!System.Windows.Forms.Label.WndProc(System.Windows.Forms.Message m) + 0xca bytes
 
system.windows.forms.dll!ControlNativeWindow.OnMessage(System.Windows.Forms.Message m) + 0xb bytes
 
system.windows.forms.dll!ControlNativeWindow.WndProc(System.Windows.Forms.Message m) + 0xbc bytes
 system.windows.forms.dll!System.Windows.Forms.NativeWindow.Callback(int
hWnd, int msg, int wparam, int lparam) + 0x30 bytes
 008d8f32()
 user32.dll!GetDC()  + 0x72
 user32.dll!GetTopWindow()  + 0x128
 user32.dll!DefWindowProcW()  + 0x183
 user32.dll!GetSystemMenu()  + 0x88
 ntdll.dll!KiUserCallbackDispatcher()  + 0x13
 user32.dll!UserClientDllInitialize()  + 0x9eb
 user32.dll!CreateWindowExW()  + 0x33
 
system.windows.forms.dll!System.Windows.Forms.UnsafeNativeMethods.CreateWindowEx(int
dwExStyle, string lpszClassName, string lpszWindowName, int style, int x, int
y, int width, int height, System.Runtime.InteropServices.HandleRef
hWndParent, System.Runtime.InteropServices.HandleRef hMenu,
System.Runtime.InteropServices.HandleRef hInst, System.Object pvParam) + 0x36
bytes
 
system.windows.forms.dll!System.Windows.Forms.NativeWindow.CreateHandle(System.Windows.Forms.CreateParams cp) + 0x247 bytes
 system.windows.forms.dll!System.Windows.Forms.Control.CreateHandle() +
0xd9 bytes
 system.windows.forms.dll!System.Windows.Forms.Control.get_Handle() + 0x31
bytes
 
system.windows.forms.dll!System.Windows.Forms.Control.CreateGraphicsInternal() + 0x8 bytes
 system.windows.forms.dll!System.Windows.Forms.Label.get_PreferredWidth() +
0x57 bytes
 system.windows.forms.dll!System.Windows.Forms.Label.AdjustSize() + 0x85
bytes
 
system.windows.forms.dll!System.Windows.Forms.Label.OnTextChanged(System.EventArgs e) + 0x1b bytes
 system.windows.forms.dll!System.Windows.Forms.Control.set_Text(string
value) + 0x6d bytes
 myassembly.dll!my.namespace.MyControl.InitializeComponent() Line 647 C#
 myassembly.dll!my.namespace.MyControl.MyControl() Line 494 C#
 (boring stuff removed)