Comment 3 for bug 1215269

So...i've had a similiar problem after updating from 3.8.0-27 to 3.8.0-29.

while booting i got a "general error mounting filesystems" with a prompt to enter the root-pw for maintanance, which was frozen so i couldn't enter the root pw. or do anything.
in contrary to your problem, the 3.8.0-27 version of the kernel didn't boot after installing the 29 version.

i read that it could be possible that the update wasn't finished, so i tried booting a live-usb stick (/dev/sdb2/ is my partition with linux)
sudo mount /dev/sdb2 /mnt
sudo chroot /mnt
sudo apt-get update
sudo apt-get upgrade
sudo apt-get dist-upgrade

didn't work.

so i tried recovery mode,
got into root console,
compared /etc/fstab with "blkid" output, everything was ok, uuid were the right ones.

calling dmesg, one of the lastest messages said: mountall segfaulted with 4 (after that 2 adresses, ip / sp, both != null)
calling mountall manually segfaulted also,
called mountall with gdb and "run", errors in dl-reloc.c 239 and rtld.c (but i don't have the stacktrace now since the problem is gone, so i can't reproduce, but more to that later)

got into root console again,
filesystem was readonly -> "mount -n -o remount,rw /"
(calling mountall still segfaults)
CTRL+D to get into recovery-menu
start networking
got into root console again
sudo apt-get update && sudo apt-get upgrade && sudo apt-get dist-upgrade
sudo apt-get clean
sudo apt-get autoclean
sudo apt-get --purge autoremove
sudo dpkg --configure -a
sudo dpkg --clear-avail
sudo apt-get -f install
sudo apt-get --fix-missing install

got no output so i thought nothing happend,

searched /var/log for hints what could be wrong. found something like "IOMMU disabled, please enable it"
reboot, enable IOMMU,
suddenly the system boots, (logging in and starting firefox, and so on)
reboot, disable IOMMU, system boots...

currently i'm not sure what it fixed, why the system boots now or if the problem is really fixed.

dmesg (see attachment), looks like filesystem is readonly again..
could the problem be a problem with EXT4 ?

not sure if i should file a seperate bug.