Topic content up from here is merged.FIX: SA/VC Mouse
I guess many of you have experienced that the mouse in either SA or VC stopped working in-game and was only movable in the pause menu. After smashing ESC several times or Alt+Tab'ing out of the game, it either works again for a little or simply freezes and crashes.
This problem occurs on computers which have multi core CPUs (so on pretty much every machine these days). Basically all you gotta do is setting the affinity of the SA/VC process to 1 CPU core in the task manager. It seems to be important that the last CPU is selected from what I tested. In my case it only works on CPU core #2 (dual core), so you might try selecting core #4 only if you're having a quad core and so on.
After applying this, the game's mouse should work all fine. Doing it every time right before playing is a little annoying, so you should save the process affinity.
Here you find several commands/applications how to do that, just pick what seems comfortable to you.
Enjoy your mouse!