Some how I would bet that you had "SIMULATION" checked in
Nero and that's why the DVD ended up bank. Oh why are you getting messages that say SCSI device? Do you have some emulation software such as Deamon Tools running?
I have no problems erasing any of my DVD+ or - RW's that I have. I always use Nero to overwrite them and I've had no problems.
Post your system specs and how you have the drive hooked up and you may also want to look in device manager and make sure the drive is properly configured.