I have been running RedHat 6.0 for a long period (over a year) and never really got problems with it. I installed RedHat 6.2 (Full Custom install) and whenever I am in X, whether Gnome or KDE, it hangs the machine completely. cannot go back to text mode console, cannot ping it from a remote machine, it's dead (no mouse either). I have a Pentium II 266, 64MB RAM S3 Virge/GX2 AGP video card
it may be the virge video card. If you have access to another video card, please give that a shot. We can't duplicate this here, and we have no other similar reports, but we know that virge video cards can be quite problematic.
The same thing happens to me. This is with a Cirrus Logic 5465 Vido Card.