Photoshop problem, lasso tools refresh

A friend of mine, a photographer and designer, recently gifted me with Photoshop 11.0 (CS4) after deciding to buy for the first time the full CS5 suite. I've been playing around with it and am actually liking the program. But I have an issue with it, I'm not sure how to fix.

While using the magnetic lasso selection tools (only happens with the magnetic lasso and the Polygonal lasso) my screen will eventually show a quick refresh and the selection gets closed. I actually can't use these two tools for more than 30 seconds without this happening, rendering the their usage a lot more difficult.

I suspect this is a problem with my video card, a ATI Radeon HD4770 and not Photoshop itself. I have the latest drivers, but would like to know, before trying to dig deeper into this problem if any of you have ever experienced it and if you found a solution.