This article is from the CD-Recordable FAQ, by Andy McFadden (email@example.com) with numerous contributions by others.
It's possible that the disc has developed a region that can't be erased.
More likely is that the software or firmware is acting up. If you're using
Easy CD Creator, insert a good CD-RW disc, and start the Erase process.
Just before you hit the final "OK" button to start the erase, swap the
troubled blank disc in place of the good one.
If this succeeds, you probably ought to run it through the erase procedure
one additional time before using it.
Super Blank, from http://www.ping.be/kris-schoofs/, reportedly accomplishes
the same thing without requiring a disc swap.
If this doesn't work, there is an (unconfirmed) report that a UV EPROM
eraser will do the trick. Experiments have shown that leaving the disc
out in direct sunlight for a couple of hours may also help. The resulting
disc won't be fully erased, but it may be "blank enough" that you can
then use Super Blank to finish the job. (Somebody else has reported that
polycarbonate is opaque to UV light, suggesting that the discs should be
left label-side-up if this is to work at all.)
If nothing at all works, make a careful examination of the write surface
of the disc. It's possible the disc is physically damaged and can't be