I have the same symptoms and have tried several approaches to finding the culprit.I am narrowing the choices down to my software. I'm using Nero 6 which is out of date (not supported). Problem appears in desktop and laptop and the only thing they have in common is the software. Interestingly I inserted a DVD RW which did not indicate the same problem but when I put it into my laptop the same symptom appeared. Wierd stuff this science. Good luck in your efforts.
hpickover@earthlink.net