Hi - thanks for the reply! I am using Studio14UC, and have previously used S12.1, but have never done DL stuff before. I have, however, successfully created both SL and DL discs in S14UC.
The problem is not with the actual burning of the disc, it is that Studio seems to create an invalid ISO image file when I create content but don't burn (this is the usual way I work so I can preview the result before committing to a burn). When I try and load the ISO image into Nero for burning, Nero says the image is bad, also when I try and mount the image with VirtualCloneDrive, it does not mount. I am guessing that when I burn a DVD it will be invalid, but don't want to waste a DL disc!
The previous DL project I created, I made an ISO file and then burnt to a disc (albeit with a few coasters but eventual success), but at least Nero accepted the image that Studio had created.
Cheers
Mark