You might try a force mount...
Launch/Utilities/Terminal and enter this command at the prompt
Press return. If it sees the disk, note the number of the disk (far left column) you want to mount.
Then, enter this command
mount /dev/(number of disk)
Put in the number no parenthesis.
If you're able to mount copy off the data you need. Even if you can mount it, wouldn't I trust the disk again.
Try Drive Genius in demo mode to run a surface scan and see if there are any bad blocks.