Burned DVDs or regular? Do they have labels on 'em?
I've noticed my ~$125 Sony DVD player has freeze/skip problems from time to time, even with new discs. Never have problems with my cheapie ($70) Philips DVD player that also plays DIVX & XVID encoded AVI files burned to disc, and never had any problems with my old $1,000 top of the line Sony DVD player back in the day, though it was old enough it wouldn't recognize burned DVDs.