Logon screen compatiblity needed for 640x480 resolution

I've had xorg.conf change to what seems to be at random to a 640x480 resolution, once when I was using the Ichthux logon screen, and unfortinately had to reinstall as I didn't know about nano and the appropriate config file at the time. Bug: https://launchpad.net/bugs/67764

Virtual Resolutions

Ctrl-Alt-+/- will change your virtual resolution. i.e. It will change your screen's resolution but not your work area so you can scroll around inside it and things. You may have to use the +/- on the number pad or the top of the keyboard. One works the other doesn't. Sadly I don't remember which it is