[holyspicoli]

I've had the same problem and it really is the worst. The only thing to do is go one by one through your backup sessions until you find one that opens up, and then rebuild from there.

I will say this to all past, present, and future encounterers of this problem. After getting hit with the error message, I started going backwards through my back up sessions, trying to open them one by one. I do a lot of "save as"'s because I'm constantly trying different things and always want to know I can jump back to given points. Well I finally got to a session that opened. Turns out the backup session that I could open was right before I did a "Save As" and started trying lots of major arrangement things in the song; moving big blocks of midi, doing a lot of trimming and editing of midi regions, and so forth. So I wonder if some amount of that, in which the computer has to start creating lots of weird little MIDI regions and such, is the cause. Seems to be logical since the error is dealing with "midi chunks" whatever that means. ProTools is pretty strange with MIDI, the way notes disappear and reappear as you trim regions and such.

Of course I have no way of knowing if that actually is the problem; it could have been some weird glitch that is undetectable and has nothing to do with that stuff. But maybe, if you have some midi in your session and are about to start serious trimming of regions and rearranging, save the whole thing to another drive, and keep closing and reopening the session as you work to see if the nightmare turns up. At least then you'll know right when it happens and have a recent backup.

good luck!