Ok, so I updated my Kubuntu 10.10 install to 11.04 and now when I log on I land in a consoile instead of getting a GUI - the rest seems to be working fine though.
I'm using a Radeon 4870 with the proprietary drivers (since the open source ones don't seem to allow some fanspeed control which gets annoying) and my xorg.conf has those entries:
Section "ServerLayout" Identifier
"aticonfig Layout" Screen 0 "aticonfig-Screen[0]-0" 0 0 EndSectionSection "Module" EndSection
Section "Monitor" Identifier
"aticonfig-Monitor[0]-0" Option
"VendorName" "ATI Proprietary Driver" Option "ModelName" "Generic Autodetecting Monitor" Option
"DPMS" "true" EndSectionSection "Device" Identifier "aticonfig-Device[0]-0" Driver
"fglrx" BusID "PCI:1:0:0" EndSectionSection "Screen" Identifier "aticonfig-Screen[0]-0" Device
"aticonfig-Device[0]-0" Monitor
"aticonfig-Monitor[0]-0" DefaultDepth 24 SubSection "Display" Viewport
0 0 Depth 24 EndSubSection EndSection
When running sudo startx I only get some error messages, see here
No idea how to solve this problem - actually not even sure what those errors mean - but I'd prefer getting around reinstalling the complete OS for a botched Xserver.