Most likely, your drive doesn't support the disc that you're trying to record.
I used to get these types of errors when I try to record Platinum 8x DVD-R discs on my Sony DRU-500 drive - which is why I looked forward to the Plextor 716.
When the Plextor 716 got released, there were various reports that it didn't perform too well, which was pretty disappointing given Plextor's reputation. Apparently, the drive was hurried to the marketplace, and Plextor didn't have the nerve to postpone its release until it could sufficiently assure its quality.
Since the initial release, however, Plextor has been working hard to improve the device; I bought one some three weeks ago, and it works great.
Your best option is to download and install the latest firmware for the drive - currently, version 1.06, which can be found
here; or, there's an unofficial, hacked, patched, region-free (a.k.a.
"RPC-1") version
there.
If you don't know what your current firmware version is, and if you don't know how to find out, then you may use the excellent and very small
DriveInfo utility - it will show you the firmware version and region status of your drive.