I use the CD/DVD burning feature of the Finder a lot. Sometimes the verification fails, but I found that it is worth it to try the 'failed' CD/DVD anyway. When this problem occurs, the CD/DVD has mounted correctly quite often. Of course, I verify it to make sure the data I added is all there and is correct.
Sometimes, it seems that the verification routine is a bit overzealous...
[robg adds: I've seen this exact situation on my machine, though very rarely. I probably wouldn't trust a CD/DVD that failed the verification step for long-term archival use, but for a simple file transfer or similar, as long as you confirm everything works, it should be fine.]
Mac OS X Hints
http://hints.macworld.com/article.php?story=20060608082017327