One of my dig cameras did the same thing last year. Nothing could reformat it (computer or camera). Had to replace it. I think the 'wear and tear' of pulling it out of the camera just took it's tole. I hope you find a solution as I have been one of the folks in the shadows keeping an eye on your project.
Good Luck!
-gruven
"The music business is a cruel and shallow money trench, a long plastic hallway where thieves and pimps run free, and good men die like dogs. There's also a negative side."
--Hunter S. Thompson