Using Audacity 2.1 on my Mac. Edited a podcast and it plays fully in Audacity as .aup. When I export it as .mp3, only certain portions of the project play. I used recorded audio for the majority of the podcast from a handy recorder. When inserting voiceovers during editing, I recorded directly into the mic. on the computer. Only the sections I recorded into the computer mic playback when I listen to the .mp3 version.