A frame shown in FullScreen exclusive mode fails to render the AWT components placed inside the frame. I am running the attached test which opens up a frame with a button. Click on the button. Frame will be pushed into FS mode. Now you will not see the button on the fullscreen frame.
Just press space bar and frame will be restored to normal mode. Do this a few times and you will notice that fullscreen window turns black.
This is reproducible only with 6u4-b01 PIT build having the D3D changes and not reproducible 6u3. Log messages show that D3D is enabled. This was reproduced with Nvidia GeForce 7600 GS with the latest driver.
Test is attached to the bug report.