I use Teon DVD+R now. Got some on special somewhere. They allow me to burn at 12X. Only difference I saw than with the other brands I used is Teon uses version 1.2. I don't know what the difference is in versions, but there must be something.

BTW I wouldn't recommend burning at the max speed, as this may lead to problems within itself.

Best of luck. I look forward to seeing what the resolution of this problem is. It will probably help many others.