[CentOS] Typing "startx" gives me a black scrren, have to reboot to get back to runlevel 3

Sat May 7 15:57:24 UTC 2011
Gilbert Sebenste <sebenste at weather.admin.niu.edu>

Hello everyone,

I have been having a vexing problem for a year, and I cannot solve it. 
Hopefully, someone has a tip to get me over the hump to fix this once and 
for all.

When I type "startx" from root, I get:

(EE) fglrx(0): atiddxDriScreenInit failed, GPS not been initialized.
(WW) fglrx(0): ***********************************************
(WW) fglrx(0): * DRI initialization failed!                  *
(WW) fglrx(0): * (maybe driver kernel module missing or bad) *
(WW) fglrx(0): * 2D acceleraton available (MMIO)             *
(WW) fglrx(0): * no 3D acceleration available                *
(WW) fglrx(0): ********************************************* *
(II) fglrx(0): FBADPhys: 0xf00000000 FBMappedSize: 0x10000000
(WW) fglrx(0): Failed to set up write-combining range 

I get a ton of stuff before this, but just info messages. Where should I 
start looking to fix this problem? I use the Redhat experimental kernels
at http://epople.redhat.com/jwilson/el5/. Running CentOS 5.6,
fully patched as of this morning with the gdb/OO updates.

Gilbert Sebenste                                                     ********
(My opinions only!)                                                  ******
Staff Meteorologist, Northern Illinois University                      ****
E-mail: sebenste at weather.admin.niu.edu                                  ***
web: http://weather.admin.niu.edu                                      **