In Redhat 5.9, when gdm starts up from runlevel 5, it
completely ignores keyboard input, which makes it rather
difficult to type in a username and password. Attempting to
switch to another virtual console (i.e., ctrl-alt-f1) does
nothing except bring up another gdm (screen flashes black
for a moment as if dropping to console, and then gdm
immediately comes up again). There's no way to get to the
console and switch back to runlevel 3, so the user is left
with no option but to reboot.
This problem also apparently happens with kdm, too. The
keyboard works fine at all other points: at the console, in
X, etc. Just not with kdm or gdm.