I am fairly certain the following issues are related, which is why I post them together, here. Something needs to be set up to make video run properly on my system but I have literally no idea what, as my experience with such things is little.
I am running Ubuntu 12.10 on the computer I recently built, and I have an R7950 Twin Frozr videocard. I noticed pretty quickly that playing full-screen video with either the default video player or VLC does not work terribly well (suddenly it has a very low frame rate), and watching video at any size via Amazon Instant Video has the same issue.
Several times since I started using this computer, I've seen errors come up telling me that Compiz quit unexpectedly. These are generally followed by a popup that tells me something about hardware acceleration and how whatever my computer is set up to do is probably not correct. I do not know how to duplicate the error, and unfortunately I cannot remember the specific text of the error.
I thought perhaps it was a driver issue, so I tried going to the following site to get a driver for the card (32-bit): http://support.amd.com/us/gpudownload/linux/Pages/radeon_linux.aspx?type=2.4.1&product=188.8.131.52.42&lang=English
When I tried to load that driver, it took quite a while and when I came back to my computer it said "gedit has quit unexpectedly." I tried it again, and the same thing happened. I am completely at a loss as to what the problem even is, exactly, never mind what to Google since I am not certain what specifically is not working.