(tentativly) disregard my last post. In an act of semi-desperation I reinstalled the operating system on our G5 this morning, and--wouldn't you know it--there are my two cards in the NI configuration app. I haven't tried running my DDK program with it yet, but I am fairly sure things will go smoothly now (famous last words I know).
For the collective knowledge of the data aquasition world, the old OS X instalation (on which NI-VISA did not seem to work at all) was set up to run off our LAN (ie you were prompted to log on to the computer, or a network account at start up), and the new instalation is just a default install with no modification to the server settings. Why this would make any difference I don't know, and it could be totaly unrelated, but it is something to think about if you find yourself with a similar problem. We have also had other mystery problems befall our networked boxes, that don't seem to afflict our un-networked computers.
My thanks to all who have assisted me in this. I deeply appreciate your help. Alan, and Geoffrey if you either of you happen to find yourselves in central New York (not somthing I would recomend mind you--esspecially not this time of year) I will happily buy you a beer. Thanks again. Cheers.
Ian Clark