garageband 11 wont convert mp3

Hi:

Project to combine 2 tracks of 25 minutes or longer.

Problem: Garageband will attempt converting mp3, and then stop. No Track.

Garageband 11, OS 10.8.2

Attempted solutions:

Converting to AIFF. Successful once, from that one on, AIFF does not even create a track.

Converting to WAV. Does not create a track.

Oddity:

Was successful in one instance, using AIFF. But, not since. Even opened successful song and couldn't import the successful AIFF as a 3rd track (used as test).