Ugh - that sounds like a really nasty error. If it's freezing the camera upon start-up, that's usually an indication that it can't even read the card as being a valid format - layman's speak, it's really hosed.
Not sure what your options are to recover the images. If the card isn't readable on camera or PC, that's the first obstacle to overcome.
When it's in a PC card reader, do you at least get the option to format the card?
As for the recovery of the images:
This is at your own risk - consider formatting it in the PC (assuming it can be done) to make it a readable card again, then seeing what the recovery software can get out of it.
The only other option is to send it off *as is* to a Commercial Recovery Service and seeing what they can find.