Updating boot support partitions for the volume as required. Back up as many of your files as possible, reformat the disk, and restore your backed-up files. I'd use ddrescue (probably available over something like macports or fink) and/or copy anything that means anything in whatever way possible and available to you (I've manually copied out files where even ddrescue failed), check disk health, then reformat the disk.
sudo fsck_exfat /dev/disk2s1 Password: fsck_exfat: Opened /dev/rdisk2s1 read-only ** Checking volume.
It seems to work fine, but when I ran Disk Utility and did a "Verify Disk", it reported filesystem errors. Apple includes Tech Tool Deluxe (a subset of Tech Tool Pro) with each Applecare agreement which is distinct to recommending it. In fact Tech Tool Deluxe has failed to detect hardware errors that Apple's Hardware test has found in my experience!
The "Repair Disk" button was disabled, because this is the startup drive. Before buying Disk Warrier, you should know that the download version of the app cannot burn a bootable DVD.
In Disk Utility the drive device was listed, but no volume could be mounted due to a corrupted partition map.
Don’t ask me how it got corrupted in the first place.
I rebuilt the structure of the drive just to be safe, and I found it did have many errors on it, which were then corrected.
Now, I take pride in having never ever lost any data on my Macs since 1998, so I was concerned this might be the end of my record…
So, I restarted with the Mac OS X Install Disc and ran Disk Utility again. You have to wait for them to ship this out, and this can take weeks.
When I run "Repair Disk", I get this output: Verify and Repair volume "Macintosh HD" Checking Journaled HFS Plus volume. Disk Warrier's website conveniently hides this information. We've reformatted the drive and re-installed everything. No backups, unfortunately (I didn't know that my wife expected me to make backups for her laptop).
I did, however, find another tool that was able to see the drive and its current file structure.