My Passport partition not mounting

Apologies if this has been addressed before:

My several years old 750gB Passport, running through the Firewire port to a MacBook Pro has stopped mounting the My Passport partition. WD Smartware still appears, so I know the drive is not dead.

No changes whatsoever to Mac OS X 10.7.5 since the last time it worked properly.

Any suggestions? I’d really like to get it working again, of course, or, failing that, to copy it to another drive.

It’s pretty well backed up, so it’s not a catastrophe if it’s corrupted beyond recovery, but it sure would be a PITA!

Thanks for any help . . . 

-Eric

Open the disk utility app and check if its recognized there.