No more data is on the tape. (0x80070450)

When trying to back-up data from a HP-Pavilion running Windows Vista - Home
Premium, using Vista's 'Backup and Restore Centre', onto it's local DVD
drive, Vista reports the following error message:
"The back-up did not complete successfully"
"An error occurred. The following information might help you resolve the
error:"
"No more data is on the tape. (0x80070450)"

I googled this 'following information' but most results refered to people
having problems with actual tape backups. I'm trying to backup onto a 8.5 GB
Double Layer DVD+R using a HL-DT-ST DVDRAM GSA-T50L SC04 177(E.

What could be the problem, and how can I resolve it?

Regards,

Rouke