is it software version 2.2? i found as soon as i put that on mine (3rd gen 15 gig) i had no end of problems.. battery went flat quicker, it turned off randomly , skipped songs, crashed..
i immediately restored it back to 2.0.1 .. works like a charm - and i've learned NOT to get sucked in by apple's promises of 'performance improvements' cause usually that means 'more crashes', well in my case anyway...
ps. same goes for version 2.1 too