Look at the message you get before entering the root password.

For example: “Checking filesystems /dev/VolGroup00/LogVol00:UNEXPECTED INCONSISTENCY:RUN fsck MANUALLY”

You then next to enter the root password and run /sbin/fsck

For example:

/sbin/fsck/ /dev/VolGroup00/LogVol00

When asck if you want to FIXED something or do something, always anser yes (i.e. y)