Re-Recording DVD+RW disks?

I have a LaCie d2 DVD±RW drive and was planning to use DVD+RW disks to (hopefully) re-record iPhoto library backups, ITunes backups, etc. I wanted to use the same disks every month, instead of using DVD+R or DVD-R disks and throwing them out.

Well, after the first record on by DVD+RW disk, I went in the next time to use the same disk and got "cannot record to disk". It thought it was write-locked and could not be reused. The Finder also sees the DVD+RW disk as read-only.

I must be doing something wrong.

Plus one other odd thing. System Profiler shows the LaCie drive as:

Manufacturer: LaCie Group SA
Model: > LaCie d2 DVD-RW Firewire
Drive Type: CD-RW/DVD-RW

Could I be missing some kind of driver update perhaps?

Thanks for any suggestions.

-- Dave