This is one of the most idiotic bugs I've ever encountered in my life.

SL5.3, netinstalled on an old laptop with a Savage video card, works
just fine, until I installed rxvt-unicode from EPEL.

Now, urxvt works when you use it, but it crashes the whole X server
when you close urxvt! (System keyboard frozen, must use ssh from a
different host.)

The key was to disable "glx", but WHY? This used to work in the past!

Details & fury: 
http://beranger.org/v3/wordpress/2009/04/03/how-can-urxvt-crash-the-xorg-

server-yes-it-does-that/
aka:
http://beranger.org/v3/wordpress/?p=1352

Of course, I can't report it as a bug. TUV wouldn't even believe it...
and EPEL is not a supported repo, no matter the bug is in "savage".

X.Org is such a mess... :-((((

Rgds,
R-C