Woohoo! Thank you wardtuk, that worked.
So, my guess is, that since the CCC was not responding properly to an attempt to "arrange", there was some condition of registry values that was present and it just choked. I think switching it to a different slot allowed us to start with a fresh registry branch for settings, and I was able to set it up without causing the pre-existing condition to occur.
Thanks again, physically moving it and starting over solved the problem.
Greg, give it a shot!
Glad to see you've cleaned it up.
I don't know what might be causing it to behave that way in the first place.
I've realized that my VISTA install is a mess - I'm getting failures on Windows Update, and the Catalyst Installer throws an error as well ("package failed" or something).
I think I might need to wipe the machine and start again from scratch. Just need to find the time.
For now, I'm back to single screen on this computer. I'm messing around with a different one at work, using 3 CRT's, and seeing similar problems. I think I'll try this "move the card to a different slot" idea there.