[CentOS] Gnome desktop trouble

Hello,

I have several CentOS 6.2 hosts (2.6.32-220.7.1.el6.x86_64) that lock up 
when attempting to use the Gnome desktop from the console.  I can always 
log in, but then all I get is the blue root window, the round initial 
mouse pointer, and nothing else.  The last process associated with the 
console is "xprop -root" which strace shows as hanging indefinitely.

There are cases (sporadic, unpredictable) when I get further; the screen 
contains desktop icons, the menu at the top, and an arrow mouse pointer, 
but the mouse and keyboard don't work.  I can reproduce this behavior 
frequently by setting the system run level to 3, logging into the 
console, and running "strace -f startx".

One other bit of information: I build all the hosts with the same 
kickstart file, and most of the hosts work fine; only a handful are 
acting up.

Has anyone seen this before and/or know how to troubleshoot it?

Thanks,
Jack