I plugged the harddrive into my old mac and it works fine in that version of DVD Studio Pro. Im very confused but I guess I will reinstall DVD Studio Pro on the new mac.
Also, I trashed the compressors settings and exported a short film and it worked fine. This is all very confusing to me but at least my dvds are burning, very very slowly, on my old mac!
Thanks for all your help, I really appreciate it!