Thanks for the reply from Alec - got a nearly usable X system now. Last problem is some nasty distortion on any vertical lines (Windows, desk top menus, etc) in the right hand potion of the screen. The standard wide weave background seems fine, and any graphic windows seem OK (I was playing with various xscreensaver modes) in this region - just the vertical lines get hosed.
This probably needs some 'tweaking' here or there, but I've tried xvidtune, etc - anyone give me some clues as to what I can try? (I am looking at 1024x768). I have the latest Mach64 server from XFree - will I have to wait for an upgrade? Is it damaging to use? (For the monitor, not my eyes....) Ed