Sorry guys, I'm a newbie...

With nero, I can burn an audio CD from MP3s without me converting them into WAVs first. I used to drag the MP3s into the CDRs with Nero and it worked fine. Yesterday I tried to do that again and it didn't work. Nero reported the CD was burned successfully but when I turned over the CD, there's no burn mark at all (just like it hasn't been burned). Then I burned a data CD with some JPGs, DOCs, EXEs etc and it worked perfectly so I guess at some point my Ricoh MP7083 looks fine. One of the weird things was, I accidentally burned the MP3s into a CD-RW and it worked (of course I can't use it in oridinary CD players). Has anyone seen this kind of problem before? Could anyone provide me with some suggestions like settings etc?

My configuration:
Duron 650 + ASUS A7V
Pioneer DVD-115F (DMA enabled)
Ricoh MP7083A Firmware: 1.20 (DMA disabled)
Windows Me + Nero 5.5.5.1 (Orion Keygen)