wxFileDialog refresh

Hello everybody,

my application:
- win xp SP 2
- wxPython 2.4.2.4
- mulithreaded python COM server
- wxPython GUI (of course) in one thread

Problem:
There is no refresh in the file-dialog of my application (wxFileDialog object) , when I change the file type in the dialog. The "dir contence widget" keeps empty.

Remarks:
If I execute wxFileDialog demo of wxPython and change the file type, it does of course the refresh.

My Idea (IMHO):
There seems to be a problem with the "thread modell" of wxPython and a callback of the Windows API, so that the cb is not called.

Any suggestions, workarounds or experiances ?

Regards
Alexander