I forced a shutdown at an inconvenient time on my kernal, and the mounting process was slightly ruined. I couldn’t find this solution anywhere, but when I tried to boot into linux (ubuntu 10.10) it froze at the busybox region of the boot process, said something about initfram, and that the partition didn’t unmount correctly. I tried ^d, no joy, it just froze a little later.
I booted with a live ubuntu disk, but it wouldn’t let me do anything with the partition, saying it was exclusively in-use by another application, or mounted (which it wasn’t), and fsck wouldn’t work, even on force.
The solution was to boot with a live ‘systemrescue cd’ available as an option on the universal usb installer and worked my way through that, ran fsck (not root/sudo required, I think it’s an auto root), and fsck could fix the problem from there. Voila.
Hope this helps someone else in the same predicament searching for the solution!