Archival DVD - Now Read as Incompatible

I'm at the tail end of archiving all of my VHS tapes on to DVD media, with a great feeling of satisfaction on how well that's gone - to say nothing of the convenience, permanence of the storage and the incredible space savings.

One of my last copying attempts included three or four movies, and literally filled the disk up to within one minute of the disk's capacity. When I went to "finalize" the disk, the system reported that the disk could not be finalized and that the disk is now being read as "incompatible". I've had this happen once before, but at least I was able to push/dub the DVD's content back over onto a tape - and then successfully re-dub it onto a DVD.

This time I don't seem to be able to even play the disc, in order to re-dub to a tape. I've take the DVD disc out and cleaned it and re-positioned the disc on the platter differently (pretty desparate, I know), but no luck. And of course, I got over-confident and have lost track of where or even if, I still have the original movie content on a tape(s) or not anymore. Any suggestions on what I might want to do to recover that DVD disc that's acting cranky?