I seem to have stumbled upon what appears to be a bad combination which causes my quest file to corrupt. I got it back after the corruption by going back to Beta 163 to save the file, and I cracked down on what seems to be causing the problem. It seems that when I save the quest with 2 midis and 6 strings, it corrupts the file. I tweaked things around a bit, and found no other things that caused corruption. Removing a midi fixed it, adding a string fixed it. Quite strange indeed. I haven't tried it on any other quests.

I can PM Dark Nation a zipped QSU of the corrupted quest. If you want me to, just say so. :)