Currently Being ModeratedAug 4, 2011 5:57 PM (in response to ChinChillaah)
I noticed the same problem. Did you use a Terminal command back in Snow Leopard to disable the rounded corners in QuickTime X? I had done that, and returning it to the default allowed me to use the Screen and Audio Recording features again. Try copying and pasting the following into Terminal (without the quotes) and pressing Return:
"defaults write com.apple.QuickTimePlayerX MGCinematicWindowDebugForceNoRoundedCorners 0".