Oh oh -- that certainly doesn't sound good
. Can you boot the machine to single user mode? If you can get into a shell in single user mode you can see what is wrong with /bin/bash and/or root's home directory (/root). Has this machine been running as a server or exposed to the Internet at all? This may be a sign that it's been compromised. It might also be a sign of hardware issues. Did you get any disk errors on boot? You'll just need to try to get to a shell (boot off a rescue CD if need be) and start looking around. You system logs might have useful details.
