Monitor not detected after booting without monitor attached (12.04)

view story

http://askubuntu.com – I had a stable 12.04 machine running perfectly. The machine was booted without the monitor connected - since then the system always boots to low graphics mode. Onboard graphics (from lspci): VGA compatible controller: Intel Corporation 4 Series Chipset Integrated Graphics Controller (rev 03) Monitor: AOC e2450Swh Display widget shows monitor as laptop(!?) and system details shows graphics as Gallium 0.4 on llvmpipe (LLVM 0x300) X-server log appears to show correct monitor detected. When I boot from a live CD I get full 3d graphics I've tried the monitor on a different machine - all OK. I (HowTos)