Unable to mount /boot anymore

[Lukas Kolbe]

Hello!

I'm using Gutsy (I know I know ;)) and suddenly can't mount my /boot
anymore. 

root at eldorado:~# mount -a
mount: /dev/disk/by-uuid/68479a21-8572-466c-abbe-21279dc24ed9 already mounted or /boot busy

What stuck me here is "already mounted or /boot busy", which is just not
true. Neither /etc/mtab nore /proc/mounts think that either /boot
or /dev/sda1 is mounted, nor can I umount them.
e2fsck thinks the device is in use, too, so I can't fsck it. 

Any hints? Here is some more information:

root at eldorado:~# ls -la /dev/disk/by-uuid/68479a21-8572-466c-abbe-21279dc24ed9
lrwxrwxrwx 1 root root 10 2007-07-13 11:23 /dev/disk/by-uuid/68479a21-8572-466c-abbe-21279dc24ed9 -> ../../sda1
root at eldorado:~# ls -la /dev/sda1
brw-rw---- 1 root disk 8, 1 2007-07-13 11:23 /dev/sda1
root at eldorado:~# fdisk -l /dev/sda

Disk /dev/sda: 80.0 GB, 80026361856 bytes
255 heads, 63 sectors/track, 9729 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes

   Device Boot      Start         End      Blocks   Id  System
/dev/sda1   *           1          31      248976   83  Linux
/dev/sda2              32        9589    76774635   8e  Linux LVM
/dev/sda4            9590        9729     1124550   82  Linux swap / Solaris

Greetings,
Lukas