This is a well known problem with Philips DR writers (especially CDD3610 and earlier). The problem is that Philips made them with components that don't last!!!
I had the same problem and when I called Philips they said that they had had a lot of this kind of problem and that they'd have my drive collected by DHL and a new one sent out to me (well, reconditioned anyway). This was done without asking for proof of purchase or that it was still in warranty (which it wasn't - I'd had it about 14 months). Three days later I got my new drive and everything works okay now.
Before you give this a try yourself, have a go at cleaning the laser (if you can do so without opening the unit) with some MINERAL WATER. DON'T USE ANY ALCHOHOL AS IT LEAVES RESIDUE ON THE LENS AND THEN IT WILL BE F*CKED!
Hope this helps!