I have an older model of that drive and I had problems that got solved by doing two things:
1) Flashing better firmware
2) Using different media if (1) doesn't help. Use Datawrite and TDK disks.
By the way I had to get a non-NEC firmware patch to get my drive to write dual-layer DVDs. Otherwise it would not recognise an 8.5 gb disc. (I initially thought it was a Nero problem, but it is not). Look for the thread Double Layer DVD, and see the link I posted for Brian. There are firmware updates for your drive that should solve the problem.