Are you saying that nothing (device or software) you have will play the MP2s except the empeg, either before you upload it to the empeg or after you download it back?

Or are you saying that it's playable on your computer before you upload it, but after you download it back, it's no longer playable? If that's the case, try uploading one and then redownloading it, keeping both. Then, at a command prompt, run ``fc /b before.mp2 after.mp3'' (replacing those filenames, obviously) and see what it has to say.