DVD+RW / Incompatible Disk

I've got Panasonic dual videotape/DVD player/recorder, which I've owned for about 7 years, and which has worked very well that entire time. The unit has the ability to record videotape or DVD, either from cable or via dubbing from videotape to DVD and DVD to videotape. I've used the unit to record directly to DVD, using both DVD-R, DVD+R and DVD-RW disks.

I recently purchased a brand new, 3-disk set of rewritable Maxell DVD+RW disks, and when I tried to initially format one of the disks, I got a message that I was using an incompatible disk - and the standard Disk Setup option was not visible on the Disk Management menu. These disks appear to be identical in type and capacity (2/4/8 hour, 4.7GB) to the Maxell DVD-RW disks that I've used previously, which are recognized and seem to work fine in the recorder. The user manual indicates that DVD+RW type disks are compatible with the recorder. Any ideas or suggestions on what I might want to do/try (besides buy a set of DVD-RW disks)?