Users are occassionally getting the above error when using our application (VB.Net, Winforms, using v2 of the framework). I'm not able to reproduce it. The callstack is as follows:

: System.AccessViolationException: Attempted to read or write protected memory. This is often an indication that other memory is corrupt. at System.Windows.Forms.UnsafeNativeMethods.CallWindowProc(IntPtr wndProc, IntPtr hWnd, Int32 msg, IntPtr wParam, IntPtr lParam) at System.Windows.Forms.NativeWindow.DefWndProc(Message& m) at System.Windows.Forms.Control.DefWndProc(Message& m) at System.Windows.Forms.Control.WndProc(Message& m) at System.Windows.Forms.ComboBox.WndProc(Message& m) at ControlEx.AutoCompleteCombo.WndProc(Message& m) at System.Windows.Forms.Control.ControlNativeWindow.OnMessage(Message& m) at System.Windows.Forms.Control.ControlNativeWindow.WndProc(Message& m) at System.Windows.Forms.NativeWindow.Callback(IntPtr hWnd, Int32 msg, IntPtr wparam, IntPtr lparam)

The code for ControlEx.AutoCompleteCombo.WndProc is as follows:

Protected Overrides Sub WndProc(ByRef m As System.Windows.Forms.Message)
	Try
		If Not m_fReadOnly Then
			MyBase.WndProc(m)
		Else
			Select Case m.Msg
				Case WM_LBUTTONDOWN, WM_LBUTTONDBLCLK
					' do nothing
				Case Else
					MyBase.WndProc(m)
			End Select
		End If
	Catch ex As OutOfMemoryException
		Throw New OutOfMemoryException("Exception during WndProc for combo " & Me.Name, ex)
	End Try
End Sub

The error handling was added so we can determine which combo causes the problem when we get an OutOfMemoryException.

Any clues as to what causes this would be muchly appreciated! :-)