This happened to Siggy in the JB thread.
He had no luck either.
If you can access your data when its hooked up to a pc then back it up. Then try the wipe option and see what happens.
Failing that i think sending it in to ASUS and seeing if they can salvage your data for you will be your best shot. Means you won't have your prime for a bit but probably the only hope you have.
If there is another way to deal with this then someone speak up but personally i think those are your only options here.