New
#11
Your unchecking the "hardware accelerator" is more than obvious regarding problems with your hardware and/or drivers.
I point out, that I use a Nvidia card and never got into trouble like that.
My guess would be problems with the AMD/ATI drivers (again).
I recently upgraded my FF from 12-something to 13.0.1.
I did not have any problems with video playback and hardware acceleration.
Look into the latest driver discussions from your video card manufacturer (AMD/ATI).
There might be several threads in their respective forums.
Have you tried rolling back a version of your drivers or do you use beta drivers (which are also causing problems somtimes)?