Mouse sometimes has difficulty moving/looking up

[CyberGhostface]

This happens even when I'm sane. Basically the mouse gets 'stuck' to a point where I can't look up. I have to either go to the main menu or switch to another window and then it's back to normal. I'm on a fairly new iMac using Steam if that helps.

[jens]

Do you have any more info on when this happens? Completely random or can you think of anything that you do/or occurs before it happens?

[CyberGhostface]

It might be if I'm walking for an extended period of time. I can't think of any specific actions.