Why is my photoshop mouse acting strangely?

[polo_tottie]

I've had photoshop CS4 for about 3 months now and it's worked like a charm the entire time. I haven't made any drastic changes to my computer - no other installations of anything but for the past couple of days the mouse has been acting strangely and it's driving me nuts. When I'm using a vector and press ctrl and click it to drag - it spazzes and shoots the line off to one side, and when i'm using a brush, it won't go where i put it and instead randomly draws elsewhere on the page, so I am constantly pressing ctrl+z every mintue having to redo practically every move i make about 3 times before it decides to do what I tell it to.

I've gone into tool presets and told it to reset all tool presets and closed it down and reopened it and it works fine for the first 15 mins and then it goes haywire again so i'm constantly having to close it down and reopen it. Any idea what on earth is going on? it's so frustrating because everything is taking about 3 times longer than it should to do!!!

My OS is win7 64 bit and i checked my device drivers and everything on my trackpad is working properly and is up to date, so i have no clue what's going on. This problem is only occuring in photoshop - every other programme I use is fine.

Any ideas?

Thanks
x