I added a monitor via the Nvidia settings tool and saved to /etc/X11/xorg.conf . When I restarted X all the WM styles seemed grey and "default" - basic.
I moved xorg.conf.backup to xorg.conf, restarted X and then it was OK.
Then I added the monitor again via nvidia settings and this time saved to .nvidia-settings-rc to my home drive.
Again when I started X I got the same problem. I even deleted completely the nvidia-settings.rc file and still the same.