Importing MP3's

HI,

i am after importing an mp3 into sonar and just doing some touch up work on it. I know this wont be the best qaulity but i am just trying to show someone what things i can do to his overall mix.

For some reason when i import the mp3 into sonar it sounds terrible. The bit rate and sample rate are the same but it just sounds aweful. Is this something i should be able to do?? WAV' are fine just mp3 suck

Any ideas