My apologies about this being a third post in a row, but I'd like to offer some information for those who stumble across this thread.
I had this exact issue happen during TiBu restore after I flashed a rom. TiBu froze up and rebooted the phone into oblivion. I manually rebooted into recovery and nothing would mount; no roms would install; and unfortunately, no backups would restore.
To solve the issue, I Googled a bit and saw two frames of logic--you need to flash the stock recovery again because this "remounts" and "rereads" everything, OR you need to go back to stock. I chose the latter.
Using Ubuntu 12.04, restoring the factory images was a piece of cake. I pushed CWM Touch (in part because I believed my prior recovery, TWRP, was not a bit too blame for things, fairly or unfairly), reset everything and here I am again, rooted with Jelly Bean.
So if you stumble across this thread, PLEASE be careful and get back to stock. It works, I can 100% guarantee it
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