When performing a RH 6.2 upgrade, if the /etc/fstab on the target HD lists a partition as containing an ext2 filesystem when it doesn't, the installer will fail. What I had done was to copy a RH 4.2 install from a drive containing three partitions to a drive that only contained two. This left the swap partition as /dev/hda2 instead of /dev/hda3. when I ran the installer and tried to upgrade the new drive, it attempted to mount /dev/hda2 as an ext2 partition. This failed. However, it should probably have a better failure method that just stopping (in the X installer) or halting the system (in the curses one).
Verified in test lab. Installer should definitely handle this situation a little more gracefully.
Should be fixed in latest internal release, passed to test lab for verification.