when I play videos on linux using VDPAU, then I see black flickering. Flickering depends on window size - for bigger window there is more flickering and in full-screen I don't see video at all). Same problem has been reported to debian bug tracking system (http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=635710
Problems started, when I upgraded from nvidia drivers 270.41.06 to 275.09.07. Version 280.13 does not fix this issue, too.
I am running 64-bit debian testing on Dell Inspiron.
1720. 01:00.0 VGA compatible controller: nVidia Corporation G84 [GeForce 8600M GT] (rev a1)