I did try to boot off it this morning when my laptop was bricked, but that didn't work. I don't know if that affected it though (I was holding down C instead of Alt so it wouldn't have worked anyway - however the Genius couldn't boot me off his external drive either). So I'm not sure if there was a problem with the back up before then or what.
Well I found some instructions relating to the "sibling" error here:
http://mahalkita.nanogeex.com/2007/0.../#comment-4386
so I tried that and got:
** /dev/rdisk1s12
** Checking Journaled HFS Plus volume.
** Checking Extents Overflow file.
** Checking Catalog file.
** Rebuilding Catalog B-tree.
** Rechecking volume.
** Checking Journaled HFS Plus volume.
** Checking Extents Overflow file.
** Checking Catalog file.
Incorrect number of thread records
(4, 22540)
** Checking multi-linked files.
** Checking Catalog hierarchy.
Missing thread record (id = 240)
Invalid directory item count
(It should be 0 instead of 2)
** Checking Extended Attributes file.
Incorrect number of Extended Attributes
(It should be 53257 instead of 53258)
Invalid leaf record count
(It should be 53475 instead of 53476)
Overlapped extent allocation (file 4 Catalog BTree)
Overlapped extent allocation (file 1172355 /.hotfiles.btree)
** Checking volume bitmap.
Volume Bit Map needs minor repair
** Checking volume information.
Invalid volume free block count
(It should be 9167124 instead of 7572373)
Volume Header needs minor repair
(2, 0)
** Repairing volume.
** Look for links to corrupt files in DamagedFiles directory.
Bus error
I'm now running it again just to see what happens the second time. It's very odd and annoying. I am just praying that the data is recoverable on the drive in my bricked laptop, because if not I am very seriously majorly screwed.