Error: Disk Utility can’t repair this disk. Back up as many of your files as possible, reformat the disk, and restore your backed-up files.
But when I ran Disk Utility again this morning, not on the Time Machine Backup, but up the hierarcy on the level labeled "319.37GB WD My Passort...," I got...
The volume Time Machine Backups appears to be OK.
And now the drive seem to be OK.
I think I'll still offload everything and reformat it.
If you've had that error message for the volume, it would be as well to do so.
Read Pondini's TM articles for how to transfer the backups;
But don't worry about the 'updating boot partitions' message in Disk Utility.
I had the same problem.
After some time I always stopped the process, thinking it is not working (was always a few hours).
Then, before contemplating to buy a professional tool, I started the process once more in the morning and left it running for over a day and a half (over 36 hours). Then, when I checked the next morning, disk utility had been terminated and the drive mounted properly.
Looks like all you need is patience, in particular if you have a big drive to fix...
With Process View you can check if the fsck process is running and using cpu capacity to make sure you are not waiting in vain...
Hope that helps