Application that uses WebBrowser control crashes after installing IE9

I've installed IE 9 last week and since, my c# .net application crashes about 20% of times. The debugger is unable to show something useful besides stopping at Program.cs Application.Run(new MyMainForm()); , btw the main form was already shown, so it's not that it's something in construction on main form.

I have Windows7.

The exception thrown is:
"An unhandled exception of type 'System.ArgumentException' occurred in System.Windows.Forms.dll

Additional information: Value does not fall within the expected range.

Screen shot of callstack -> http://img861.imageshack.us/f/ie9v.png/

When running outside of debugger, this info is shown:

Problem signature:
  Problem Event Name:   APPCRASH
  Application Name: myexe.exe
  Application Version:  6.7.6.0
  Application Timestamp:    4d7fdffd
  Fault Module Name:    mshtml.dll
  Fault Module Version: 9.0.8112.16421
  Fault Module Timestamp:   4d76266c
  Exception Code:   c0000005
  Exception Offset: 0012c848
  OS Version:   6.1.7600.2.0.0.256.48
  Locale ID:    1037

And sometimes instead of mshtml.dll it says StackHash_f09d

Problem Event Name: APPCRASH
  Application Name: myexe.exe
  Application Version:  6.7.6.0
  Application Timestamp:    4d7fdffd
  Fault Module Name:    StackHash_f09d
  Fault Module Version: 0.0.0.0
  Fault Module Timestamp:   00000000
  Exception Code:   c0000005
  Exception Offset: 00000000
  OS Version:   6.1.7600.2.0.0.256.48
  Locale ID:    1037

Thanks in advance

Edited:

That's what I see in windbg, with symbols:

0:000> kb
ChildEBP RetAddr  Args to Child              
0020eda4 64d54f83 0566c988 00001012 00000000 mshtml!CDoc::ReduceMemoryPressureTask+0x1a
0020edb4 64d54f2c c6b991e4 0020ee78 00000113 mshtml!GWYieldToMsgOnCurrentThread+0x17b
0020edfc 770086ef 00192392 00000012 0000201b mshtml!GlobalWndProc+0x1f2
002