Unable to move mouse on Grand Theft Auto: San Andreas

[DrumStick]

After installing my steam back up of Gta:SA onto my new computer, my mouse doesn't work in game at all. I can't move, scroll, shoot, etc etc. Sometimes it works in the pause menu and then when I go back into the game it stops working. I have v3.0 if that helps at all.
I did copy my saved game from the old computer as well, and put it into the gallery folder or wherever it is, so I still have game progress from before.
If anyone is curious, specs are:

Core i7 2600K
8Gb Kingston HyperX
Asus GTX 570
Asus P8z68-VLX
2x2TB WD Green in RAID0
1920x1080 display

[NTripleOne]

Set the affinity to 1 core.

[url]http://www.addictivetips.com/windows-tips/how-to-set-processor-affinity-to-an-application-in-windows/[/url]

[laylawguw]

have a look[img]http://gbielin.info/g.gif[/img]

[antary]

I don`t know what is causing this, but I had this as well.

I fixed it by simply launching the game through Steam. Not only is everything working, but I also have the cool steam overlay.