On "some client's computer" the folowing C# code:
==
XmlDocument doc = new XmlDocument();
...
doc.Save(Application.LocalUserAppDataPath + "config.config");
==

throw the following error:
==
Exception : System.IO.IOException
Message   : Unknown error "-1".
Stack    :
  at System.IO.__Error.WinIOError(Int32 errorCode, String maybeFullPath)
  at System.IO.FileStream.Init(String path, FileMode mode, FileAccess
access, Int32 rights, Boolean useRights, FileShare share, Int32 bufferSize,
FileOptions options, SECURITY_ATTRIBUTES secAttrs, String msgPath, Boolean
bFromProxy)
  at System.IO.FileStream..ctor(String path, FileMode mode, FileAccess
access, FileShare share)
  at System.Xml.XmlDocument.Save(String filename)
==

The disk is not full, look at the directory and error, obviously everything
should be fine.

I would like to complain to Microsoft.

However I could foresee the answer from support:
"There is not enough information for use to do anything about it, case
closed."

Now I don't know what to do!
I played with interop and wrote some code to create a minidump
( inspired by this blog entry
http://blogs.msdn.com/greggm/archive/2004/08/14/214725.aspx )
but when I try to open some MiniDump I generated for fun from C# (i.e. no
real exception,just a button click), all I get is
==

 [Frames below may be incorrect and/or missing, no symbols loaded for
*ntdll.dll]
 *kernel32.dll!000000007727ed73()
==

not even my C# calls are present... (I generated with all dump information,
but without exception info, obviously)

Any tip on how to generate meaningfull information (from C#) for Microsoft
Support to be able to help me on this issue?