Hey Benshee, I feel your pain. BELIEVE ME! I am assuming that you have an 05 GTO correct?
I had a problem when I tried to upload an 05 program into my 06 GTO, It got to 3% and stopped, and then wouldn't up load my old config. I didn't start my car for 5 days.
I called Diablo Sport, explained my problem and they said to send them the Predator (w/my VIN number) and my PCM(out of the GTO), They flashed my PCM to the newest GM updates AND reflashed my Predator with the Factory/91Octane/(and)Diablo Tune.
I'm good to go now...
PM me if you need help or more info