Every once in a while my xorg.conf resets without a clear reason. I'm working normally on the desktop, when finished i switch of my pc and when I restart it I have to run nvidia-xconfig from within tty1 and do a /etc/init.d/gdm restart afterwards to launch the desktop. What logs and where are they should I check to see what's going wrong?

I'm using Ubuntu 10.04 AMD64 I have installed the latest nvidia propietary drivers using Ubuntu Hardware Drivers manager. My graphics card is an integrated geforce 6150