Jagged brush problem

[daadaa]

Hey, im sure this problem must have cropped up before, but i cant find any solutions that solves my problem.
I dont recall having this problem before, but i cant remember when this problem started either. Ive looked around, and the solutions people suggested are to just update drivers, which i have done but makes no difference in photoshop.

i cant seem to get a smooth line, curves or straight line. With/without smoothing enabled. Smoothing helps but the quality is still really bad.

http://img64.imageshack.us/img64/9682/jaggedproblem.th.jpg (http://img64.imageshack.us/i/jaggedproblem.jpg/)

Uploaded with ImageShack.us (http://imageshack.us)

Uploaded with ImageShack.us (http://imageshack.us)

i dont think its a problem with my computer either but specs are:
i7 920 @ 4ghz
12gb ram
Nvidia GTX 280 graphics card.
Wacom Intuos 3
Photoshop CS5 Extended

Does anyone else have this problem?
any ideas what i could do?

Thanks

Da