Jeffery,  The information that it is a mutex string is helpful and
I performed some additional tests to try to get more information.

On a second system,   XP Home without  VS2005 - Application works.

ExceptionType: UnauthorizedAccessException
HelpLine:
Message: Access to the path 'Global\.net clr networking' is denied.
StackTrace:    at System.Net.Sockets.TcpClient.Connect(String
hostname, Int32 port)
  at RemoteInterop.RemoteInterface.ConnectToMasterController()
  at RemoteInterop.RemoteInterface.StartDownload(String profileName)
  at StartDownload.Program.Main(String[] args)
TargetSite: Void Connect(System.String, Int32)

  The client socket gets as far as the network connect because the
server socket sees a connect, followed by an immediate disconnect
without any data.

  Here's where it gets interesting.   The system with the problem is
Windows 2000 Professional with the login having only normal user
privileges (not administrator).   Caspol.exe doesn't run in the normal
user account, so we logged in as administrator.  The application then
worked without the Caspol.exe setting.   So it seems that a normal
Windows 2000 user account lacks some privilege required for access to
the mutex 'Global\.net clr networking'.

  I created a 'limited user account' on Windows XP Home, but the
application works there, so I was unable to narrow the issue further.

  How do I find out what privilege is required for a limited Windows
2000 user to access the mutex 'Global\.net clr networking' ?

  Thanks,

  Jeffery

More information -
    1.)  The socket server task also dumped with a much more
informative stack trace.   This is included below.
  2.)  Someone else had the problem and posted in this newsgroup. The
only thing in common was German Language, Windows 2000, and running as
an ordinary user.   They solved their problem by going to XP.

   Eventually, more people will encounter this problem.  A
shrinkwrapped app cannot require the user to upgrade to XP.   Perhaps
the shrinkwrap vendor can revert to the ugly mode and say 'our app
requires administrator privilege under Windows 2000'.

----------------------------------------------------------------------------------
ExceptionType: UnauthorizedAccessException
HelpLine:
Message: Access to the path 'Global\.net clr networking' is denied.
StackTrace:    at System.IO.__Error.WinIOError(Int32 errorCode, String
maybeFullPath)
  at System.Threading.Mutex.<>c__DisplayClass3.<.ctor>b__0(Object
userData)
  at
System.Runtime.CompilerServices.RuntimeHelpers.ExecuteCodeWithGuaranteedCleanup(TryCode
code, CleanupCode backoutCode, Object userData)
  at System.Threading.Mutex..ctor(Boolean initiallyOwned, String
name, Boolean& createdNew, MutexSecurity mutexSecurity)
  at System.Diagnostics.SharedUtils.EnterMutexWithoutGlobal(String
mutexName, Mutex& mutex)
  at
System.Diagnostics.SharedPerformanceCounter.Verify(CategoryEntry*
currentCategoryPointer)
  at
System.Diagnostics.SharedPerformanceCounter.FindCategory(CategoryEntry**
returnCategoryPointerReference)
  at System.Diagnostics.SharedPerformanceCounter.GetCounter(String
counterName, String instanceName, Boolean enableReuse,
PerformanceCounterInstanceLifetime lifetime)
  at System.Diagnostics.SharedPerformanceCounter..ctor(String
catName, String counterName, String instanceName,
PerformanceCounterInstanceLifetime lifetime)
  at System.Diagnostics.PerformanceCounter.Initialize()
  at System.Diagnostics.PerformanceCounter.set_RawValue(Int64 value)
  at System.Net.NetworkingPerfCounters.Initialize()
  at
System.Net.Configuration.SettingsSectionInternal..ctor(SettingsSection
section)
  at System.Net.Configuration.SettingsSectionInternal.get_Section()
  at System.Net.Sockets.Socket.SetToConnected()
  at System.Net.Sockets.Socket.UpdateAcceptSocket(Socket socket,
EndPoint remoteEP, Boolean needCancelSelect)
  at System.Net.Sockets.Socket.Accept()
  at System.Net.Sockets.TcpListener.AcceptTcpClient()
  at mcSimulator.RemoteControl.RemoteServerThread()

TargetSite: Void WinIOError(Int32, System.String)