Make sure they are 'real' mp3's. Check Virus thread: Typical virus spam file sizes - Make a note of them (click on blue link to see) to be sure none of yours match those sizes as they are probably not real mp3's. Play all the songs you wish to burn, see if they all play ok.

May be a problem with your burner codecs not being up to date & not reading the mp3 format properly. CODECs list for Movies/Audio/ Alternate players / Video help forums/ video-mp3 fixers. Personally I use a dedicated disk burner program.

When burning an Audio CD, always burn at minimum speed possible. If possible, choose a low speed disk, not one of the super fast 45 x speed ones.