If your still under warrenty your best bet is to make use of it, go and get it checked by the manufacturer.
Before you do though, it might be worth checking your disks, buy some new blank disks from a well known, respectable company and try them.
I recently had a similar problem with some cheap and nasty blank dvd-r's, so I tried using HP ones and they worked.
When I looked at the cheap ones, there was a circle on the disk, I tried to burn, it burnt to the circle and no further, wierd, HP had no circle, no problem. I can only assume I got a bad batch.