Cannot select disc-at-once

This is strange. I’ve been using NTI 7.0 Platinum to burn DVD’s using disc-at-once. After about 8 DVD’s “Disc-at-Once” is greyed out. I then tried my Nero 6.6, same thing.

I’m using a Mad Dog 12x DVD burner. Thinking it’s the burner, I purchased a new Mad Dog 16x DVD burner.

Same thing.

I’d updated the firmware for the 12x burner Dec 2005. I don’t think the problem is either the software or hardware.

I think it may be registry error, but have had no luchn in finding any help on how to roubleshoot the problem.

Any help is greatly appreciated. Direct email sugestion is welcome.