I do not have a Radeon myself, but i am using a laptop with a Neomagic chipset. 
Xfree 4.2.0 gives the same problem, but also segfaults on me.  This is a current
thing that began happening after a cvs update (last night actually).  My last
update had been a few weeks ago (takes 9 hours to run make build in entirety).

All that is in the XFree log files other than the usual configuration stuff is
"Caught signal 11.  Server aborting".  Then it returns to text mode with
very dim characters.  I might be thinking the wrong *BSD, but is there a 
"machdep allow apperture" that must be enabled to run XFree?  I don't see that
in my config file, or i overlooked it.

Ross