Screen turns black and back to normal after installation of 11.4


I had 11.3 running for quite some time without any problem. The upgrade to 11.4 was ruined for some reason (only got commandprompt login) and the message that Xorg.0.log couldn’t be copied. Decided to install 11.4 from scratch, but since the install my screen flashes every 20 seconds or so to black screen and and after 1 second back to normal. There is no interruption of any other task like typing. Card: FeForce FX5200 card. Can someone please point me to a solution?
Also, my monitor (Philips 150S) is not recognized. How can I change that without changing xorg.conf by hand?


What happens when you simply make a backup of xorg.conf and then remove that file and reboot ?