When installing RedHat 6.0, I've received the error "'mount failed" two different times. Your online FAQ mentions some possible solutions, but both times for me it's been because I forget to hit the space bar to select my root partition to format (/dev/hda1) in my case. You really, really should mention this in your FAQ also.
We now default to formatting the root partition on installation, so this is much less of a problem.