"Thanks to Roy, we've found the problem, and getting back to printing does not require a re-install. After double checking all his saved settings, it seems the color matching setting had changed from quadtoneRIP to colorsync. After setting that back again, it worked. The next steps are to determine whether or not interim color/OEM driver printing "unsticks" that setting and reverts it with his particular OS, PS, QTR versions... will let you know. For now the main thing is, if QTR stops working for no apparent reason with a simple "error" alert, take a look at the color matching setting.. it's not a setting I would have been terribly careful about, or suspect of these problems. But given the current OSX colorsync debacles I guess it's no surprise."
I've tried all of the suggestions above, but no positive results yet. I also tried the routine of selecting a different resolution in the driver and then returning to the one I want, but again no printing happening. Just wondering if there might be another approach which I haven't been able to find in the archives.
I'm using version 2.7.5 on a Mac Pro and OS X 10.9.5.
Any replies would be much appreciated.
Gary