You may want to try converting to .wav first (and then defragging) before burning. When Nero (or ECDC) converts mp3 to wav during on the fly audio CD burning it has to put the wav data into a temp file and then burn it to the CD. That's a lot of I/O activity happening on your hard drive while burning and fragmentation can become an issue, not to mention the extra strain on your system resources for the conversion. On-the-fly burning for audio is generally not recommended by most audio CD guides I've read.
Several audio CD guides also suggest burning audio at 2x speed only, regardless of how fast your burner is. I've followed those guidelines religiously and haven't made a bad audio CD yet
I've read that burning audio is a more complex mathematical process than burning data only and there's a greater chance of errors the faster you burn audio. It takes a little longer but the extra time has been more than made up for by not wasting time making coasters and having to burn it all over again.
Good Luck
JohnE.