My mouse always seems jittery, it's not really noticable outside, but when I'm indoors, close to a wall or (sometimes) a person, my mouse seems insanely jittery sometimes, I've tried a number of fixes, including:

D3DOverrider
Turning off mouse acceleration
Turning off vsync
Triple buffering
Lowering sensitivity.

I've mostly fixed the problem by limiting my FPS to 60 in Dxtory, to the point where it's still noticable indoors, but alot less noticable and jittery.

Has anyone else had this problem?

By jitter, do you mean wobble about a bit or stutter in an unresponsive way? My mouse started to stutter a bit today. I'm not sure if it is a Skyrim specific issue though since it just did it on the desktop. But that was only once.

I don't mean to hijack your thread with a semi related issue but my keyboard regularly locks up while playing Skyrim, and occassionally stutters a little while using other programmes. It does it alot when I am playing my second favourite game, Spider solitaire.

Not exactly, it feels more like it just moves in a stuttery/jagged way.