Hi Paul, I have just come upon your post - I do not come here too often as I have other work to do also. It seems strange that the system crashed on an XP machine as I have the program installed on an XP machine myself and have not had any problem like that. I do not use the rulers at all but this could be a units issue where they need setting, go to Options/Drawing Setup and then navigate to Space Units. Snaps. Right click Snap in the lower right of screen and open the Snap dialogue box, at the top of this box in Modes, place a tick(click) in the box next to No Snap. That should fix it.
Paul, this program is not very 'buggy' and is based on TurboCAD and if your an old Autodog user, it is a little 'buggy' to get round until you get the feel of it. It does not take too long. I know this as I am also an old hand at Autodog from v 2.5, a user (and still a user of) of SolidWorks and a user of DesignCAD. The program is not crap.
if you click on my name, send me a PM (personal message) with your private email and I can help you out.