hmmmm...had it happen to me on one CD once! Turned out to be condensation on the disc after a really cold night! Took it out and wiped it with a CD cleaning cloth and all was ok.....trouble is, not sure why it would do it on all of them....??

Might have been some dirt on the CD players lense.
Other than that, get it down to the dealer if its still happening!!
Cheers - Neil