I've just had just about the same problem the other person here has had. Only slightly different hardware and software configs.
I've been using A05 since the day i brought it home. Its in a Firewire/USB2 External case (Metal Gear, from fry's, which works with my harddrives if i switch out the burner) and:
XP Pro SP2
Nero 7 (ultra)
It will sometimes write CD Data but not CD Audio (ever) even an image of a CD Audio. It copied CDs (data) and wrote ISOs... and any kind of DVD that i ever wanted to.
Just in the last two days, i have one through about 5 coasters (in the true techsup style, testing out all possible problems...) and it won't even burn DVDs now, even though i have burned 3 DVD coasters EVER before today. and none were from the 100 spindle of Verbatim 16x's that i'm using.
Well... it reads everything fine, and AnyDVD works to copy stuff to the computer, but even if it is disabled, it doesn't want to write anything back to DVD. Data, Video, Audio CD, Data CD, anything.
are there any cure-all windows standard replacement drivers out there? That would be useful.