i’d say it has something to do with your mouse

With out looking at it, I’m gonna take a stab and say I’ve gotten it a billion times before.

If you move your mouse sharply, or lift it and hit it firmly – not too hard! – on your desk/mousepad, it should fix up. I think that it is caused by a piece of foreign material getting into the laser/whatever bit of your mouse that screws it up. I’ve only ever encountered it in ET though, no other games or in general Windows, so it’s just as likely that it’s an ET issue.

It disappears for me within 4 seconds, though it’s gotten me killed a billion times before.

Double check you don’t have a spin bind though?

Or if it’s wireless and your using a wireless network it could be the two signals interfering each other.
Chiefly the internet screwing up the mouse.
Had that problem caused me to snap right up or right down. Took me a while to solve the problem.
To fix that just make the mouse receiver closer to the mouse.

Thanks guys for the replies. I don’t have a wireless mouse.

I ended up doing a restart and the problem resolved itself.

Thanks again.