Nothing, the same problem. In /var/log/Xorg.0.log i don't find any error or somethink unusual.
Code:
(II) LoadModule: "radeon"
(II) Loading /usr/X11R6/lib/modules/drivers/radeon_drv.so
(II) Module radeon: vendor="X.Org Foundation"
compiled for 1.9.5, module version = 6.12.2
Module class: X.Org Video Driver
ABI class: X.Org Video Driver, version 8.0
(II) RADEON: Driver for ATI Radeon chipsets:
etc...
I will wate 5.1 and then I'll try.