Many times repairing those kinds of situations in Linux is as simple as:

- boot linux livecd

- mount your broken filesystem

- bind mount the important bits from the live kernel (/proc)

- chroot

Like this:

    cd /

    mount -t ext2 /dev/sda1 /mnt #Here's your broken install

    mount -t proc proc /mnt/proc

    mount -t sysfs sys /mnt/sys

    mount -o bind /dev /mnt/dev



   chroot /mnt /bin/bash #boom you are in.

Now do whatever you can to repair the system. depends on what broke.

usually apt stuff for me(pulled power during a package upgrade)?