Audio MP3 CDR not playing on Plextor 712A DVDRW

Plextor 712A, Firmware 1.05. It can play storebought audio cds fine. It cannot play mp3 cdr’s (burned at 52X, Memorex CD-R) which my cdrw can play. Is this to be expected?
WinXP Home, tried WMP, Media Player Classic, and Ultraplayer.

Is this to be expected?

No … but can you be more specific? Did you use File|Open with MPC/WMP, and what did they say when you tried? Can you read the directories of these discs in Win Explorer? Are the burns any good (try C1/C2/CU scan in Plextools)?

My bad, it was bad burning on my part. I downloaded some mp3’s from another source and burned them. I tried the two cd’s that would not play in a portable player and they did not play.