happend to my first hammerdin way back in Beta right after rag put out his guide(like the week it was out Heh)...had a lot of nice stuff too...ended up deleting him but i never did ask anyone if there was a way to recover so...hope someone can help ya...kind of a bummer
As NF has already said, look through the .Org files that should be in your save directory, these are ATMA backups of the character, then rename them as character files. You might loose a few levels but its better than nothing. Be sure to check the character for dupes of items you'd already muled off to Stashes.
This happened to me just as my Fishymancer was about to enter Nightmare for the first time. I lost a good 10 levels :grr: I think its something to do with Windows scan disk... it only seems to happen when that runs at startup and decides part of teh save file is in the wrong place or somesuch.