During gameplay, character models will walk and run around slowly, as if through a viscous invisible fluid, and the music and ambient sound sputters rapidly. It sounds like when you talk into a desk fan, if you know what I mean. The weird thing is that speech and dialogue plays just fine, so I don't know what the problem is. I don't know where to begin with providing extra details, so if more diagnostic info is needed, ask.

Windows 7 x64

{EDIT}
Ok, so here's what happened. Through trial and error, I found that turning OFF Catalyst AI caused a whole bunch of character models to disappear during gameplay. When I turned AI back on, the models reappeared. As for CPU Affinity, I found that turning on CPU Affinity for ALL four cores on my machine (Phenom II X4) actually cured the stuttering and slowframe problems, when used with the "Miles 2D Sound" option.

My only problem now is that all "non cutscene" movies won't play. That is to say, they aren't visible, even though I can hear their audio track.