Steve Gibsons program Spinrite has helped me on several occasions, but more far hard drive damage and I haven't tried
it with an external firewire drive.
It has recovered stuff when nothing else could.
http://www.grc.com/spinrite.htm
Once you get by this though , you need a good backup program to save your stuff so this doesn't happen again. I would suggest Acronis True Image which can be setup to image your entire drive to DVD.
Good luck....!
