Ouch!
I've had similar problems in the past, both with FFS and SFS. I think something must get corrupted in the RDB as the first thing you know about it is the visit from the Guru when trying to reboot.
The only think that seems to sort it is to make sure you do a FULL format of your partition before you install anything on it. It may take all night, but prevention is much better than cure, especially when talking about your files.
