I had this happen a few months ago to an external hdd, I was stupid enough to plug it into a pogoplug to try doing a san on the cheap. big big mistake, never ever use a pogoplug.
anyhow, mine was showing up as unreadable RAW. I used the Ultimate Boot CD and was able to get 100% of everything back. it even pulled the tables and recreated the folder structure without a problem. the other tool I had tried prior to UBCD could only pull raw files off, named 001.jpg, 002.jpg, etc. which sucks.
Ultimate Boot CD - Overview