Ok, this is a bit hard to explain but here goes.
I really don't know what mouse acceleration is because I haven't experienced it myself, but something is happening that might be related?
I seems to happen ONLY in MMOs, so far I've seen it do it with WoW, Wildstar and Guild Wars 2.
Basically everything is working fine and smooth, but then all of a sudden my view changes INSTANTLY to somewhere I wasn't looking.
So I might be running with my character forward and all of a sudden I'm looking at the sky.
It doesn't happen constantly either, just a random intervals and seems to be with MMOs since I haven't noticed it on other games.