DVD+-RW won't read burned data DVDs

Hi Guys,

From what I can see trawling the internet this is a common problem:
I just swapped my DVD drive out for my girlfriend's because hers is black and goes with my case. I've just figured out that the drive has a peculiar problem. It will recognise and play game DVDs, it will recognise movie DVDs (I don't have a decoded program so don't know if they play), it will play game CDs and music CDs, it will even play burned music CDs. But it will not recognise any burned DVD.
The drive is: hl-dt-st dvd+-rw gwa4164b. Her PC is custom built so I don't know who it was supplied by but I suspect it came out of a Dell or some such pre-built PC as it was popular (and problematic) in them.
I have uninstalled the windows drivers and let them reinstall and this didn't work. I have upgraded the firmware from E111 to E113 and then down to E112 (all from Dell's website) with no joy. I deleted the Upper filter registry key that someone suggested in another post as well.
The one thing I have tried that no other post I have read has is try it in another PC, because it had problems in my girlfriends PC but she never noticed and thought that the problem was the DVDs themselves.

It seems a bit bizarre. The driver itself does not play burned DVDs, I guess it could be a anti-piracy thing but I think that's unlikely because there are so many legitimate used for burned DVDs. The ones I can't get to work are all backups of photos and documents.

Any help much appreciated.

TIMEWARRIOR