BackItUp not using available disc space


I’m trying to backup some documents using BackItUp (v1.2.0.18 came with Nero6). My data size is about 900MB. I’m using blank DVD+R (and have also tried DVD+RW). Everything is going fine until it prompts for a 2nd disc about 400MB into the job. I can only imagine that it thinks its a CD and breaks it into smaller pieces. The “Target” drop list only features CD and Hard Drive… obviously CD is the closest bet but makes me suspicious this is the problem. I have tried inserting the same disc… it gets a bit further then asks for disc 3! Clearly the 900MB should fit on a 4.7GB DVD…

Any ideas appreciated.