I have a laptop with X1350 and an external SyncMaster T240 with 1920x1200 connected via DVI.
Using the proposed standard xorg.conf from http://www.x.org/wiki/radeonhd all monitors are black, no response or restart of X server possible.
When I delete xorg.conf, the X server starts both monitors work with the execption that the external cannot be switched to its native resolution and the "radeon" (kernel?) driver is loaded.
Created attachment 31533 [details]
(EE) RADEONHD(0): RHDMCSetupFBLocation: Cannot setup MC: not idle!!!
Standard issue, which unfortunately isn't fixed yet. AFAIR radeon doesn't test for MC idle, dunno whether you can have issues from that or not.
Comment on attachment 31533 [details]
MC lockup issue.
Does this issue occur with the preferred ati driver (xf86-vide-ati)? If so, please move this to the Driver/Radeon component.
Development of radeonhd has pretty much halted and development focus is on the ati driver. Please see http://www.x.org/wiki/radeonhd
If the issue does not exist in the ati driver (or if there is no response to this message), this bug will be closed as WONTFIX unless someone contributes a patch.
Closing due to lack of response. Please reopen and move to the Driver/Radeon
component if this issue persists with xf86-video-ati