My guru buddy just got through with two days of re-installing XP-64, XP-Pro to try and eliminate a hanging problem with DVD-A4 and Vegas 7.0 while accessing the burners. The problem was a Lite-on DVD rom being identified as a cd rom by windows. This would cause DVD-A and V7 to hang when trying to access the other burner in the system. So he pulled the lite-on out of the system and everything was OK. Since the DVD-rom could not be accessed new firmware could not be implemented. I think he trashed it after a Pepsi and a smoke.
JJK