hi benjaminDid you try without dri? (Comment out dri in the X config file)
now i had some spare time to do some investigation
booting the 2.6.11-rc5 with radeonfb.default_dynclk=0 or with -1
brings up a framebuffer console. everything is fine.
starting xorg-x11 with Ati binary only drivers just brings up a black screen
without a mouse cursor and freezes the hole machine. even network ect. is no more reachable from outside the machine. worst thing out of that
a tail on the log files (on another machine) does immediately stop - also no output is written to syslog :/
next scenario - test 2.6.11-rc5 with radeonfb.default_dynclock=0 and -1
starting xorg-x11 with Xorg Radeon driver. a grey screen comes up - mouse cursor is visible and also able to move for
5 - 8 seconds after screen display - then freezes the whole machine again.