Zion, I had a problem with my Ti4600 a few months back. Not the same as yours, but my games would freeze for 10-15 second and then start up again for a few minutes until freezing again. Very annoying. Anyway, I fell back on the classic NES-fix of opening up my case and blowing the dust out of my video card's heat sink and that seemed to fix things up. You might want to pick up another case fan too, if overheating turns out to be the problem.

If not, pricewatch.com lists a number of cheaply priced replacements.