7.5.508 on Windows XP SP2. This is on behalf of my parents who recently purchased the 7.5 upgrade. If you need things like log files I will ask them to contact you but they are pretty computer-averse so I wanted to try to get an answer for them.
When we started out, they had Retrospect 6.5.
They have a Dell Optiplex (not sure the model but pretty recent) and a Samsung Super-WriteMaster, SHS203 DVD writer. I installed it for them and went through the device configuration, which was successful.
However, at the point Retrospect should have started writing to DVD, an error displayed ... I don't remember the exact error, maybe "trouble writing".
In the error dialog box, I clicked on the disk and then clicked Proceed, after which I got an error saying the disk was write-protected. This happened several times in a row (IOW, I deleted the device configuration, reconfigured, tried to back up). And I also changed discs several times.
I did not try writing to the disc using another application, so the DVD writer might be the problem. However, it's very strange that Retrospect would successfully configure the device (which presumably involves writing to it) but not be able to back up to it.
P.S., at some point in an attempt to fix the problem, I got them to upgrade to 7.5 but that had no effect.