can burn CDs but not DVDs with DVD burner

I have been having problems burning DVDs in Windows XP Home SP2.

Originally I had a Samsung TS-H552 dvd burner. It came with Nero 6
which I installed. It does fine burning CDs and CDRWs using Nero or
Windows native software. When I insert a blank DVD+R, the drive name
in my computer changed from "DVD-RW Drive" to "CR-ROM Drive". If I use
Nero to try to burn the DVD, it recognises the DVD, knows it is blank
and says it is ready to burn. When I start the burn process, it fills
the buffer and then just hangs without ever burning the DVD. I'm at my
wit's end with this problem.

I thought the drive was bad, so I bought a brand new BENQ DVD Burner
and it has the EXACT same problem. I've tried other DVD burning
programs as well including Nero 7 and Roxio 7 and easy DVD video copy
and none of them work. I've also tried about 6 different brands of
media and nothing works. PLEASE HELP!!!