trying to "bounce" softwate tracks to MP3 and/or .wav file. MP3 and .wav show up on my desktop, but files contain NO DATA (even though "get info" says there is data and shows a file size). Any ideas?

Have you tried exporting individual tracks as audio files, or have you just bounced down to a stereo file? If the info window says there is data, how do you know the files contain no data? And how much data is supposedly in the files? When you try to play them in QT or iTunes, what happens? Did you click in the arrange area to deselect all regions before bouncing? (If you accidentally have a single region selected somewhere Logic will only bounce that part of the song.) Are the volume faders in the mixer turned up?