>  - every time I mounted it, I got messages asking me to fsck it.
>  - when I fsck'd it, nothing was wrong, it asked if I wanted to mark it clean.
>  - I typed 'y' to mark it clean, it said the filesystem was modifed.
>  - I then umounted and remounted the filesystem.
>  - it still said it was unclean and asked me to fsck it!

I think what's happening is (and this is only a guess):

- You mount filesystem, loading buffers/superblock into memory.
- You fsck filesytem, changing on-disk contents.
- You unmount filesystem, writing back bad buffers and superblock to disk
- Goto step 1

I don't  think this is a new problem; as I understand it, this is why
the -n option exists for reboot.

--Ken