Aquestion about DirectShow, win32 API...

I am doing a project by using DirectShow, win32 API and ATL.
I created a black static frame in dialog box to display the video.
In the dialog box I also created few push bottons such as play,
pause, stop, etc. Every function goes well except when I clicked
pause or stop button and switched to another window such as IE, then
back to the video window again, I cann't see the paused video player
picture, only the black static frame. How to fix this problem. THANKS!