I have a Pioneer CLD-V2600 and I have a similar problem.
It will read LDs but will not even recognise a CD. Could be an issue with the pick up but from what I have read already, it's un-economical to replace the pick up as it has to be re-calibrated and aligned which is very hard to do.
I've also got another problem with my player...
When it plays the LD, the picture is very fuzzy - any ideas what is causing this?