Audio cd problem with some tracks....

[Djdat]

I use deepburner free for audio cd's a lot with no problems. However, I have an issue with certain mp3 files at the processing stage before a burn. It says "null" for these tracks and the burn continues,but nothing is heard on the disc afterwards.
My question is what is this "null" and what does it mean? The mp3 plays fine everywhere else (mp3 player,pc etc) And on it's ID3 tag it is not protected.