I have a Sony DVD player that is probably 8-10 years old.  I have noticed that even on new DVD's, it was beginning to skip.  I had heard of VCR head cleaners but never knew that there was such a device for for DVD and CD players.  When I was playing my new Season 5 "The Office" DVD and the first one was skipping, I was frustrated.  I took a look at the DVD and made sure there were no overt scratches or dirt on it.  There were not.  The problem kept happening.