To repair any damage done to your filesystem, you will want to run fsck *from a live cd* on your partitions. For example
sudo fsck dev/sda1
sudo fsck dev/sda2
Regarding the freezing, please tell us which computer you have. There is a freezing bug that requires some kernel parameters to be installed in your menu.lst. If this is the case, you would experience occasional stalls when booting your computer as well.
If this is not the case, give us more info on the configuration of your system: how much ram, what cpu?