Thank you for the advice! After reading the FAQ's in Gimp-Print's web page I learned that some applications (mostly Carbon apps) need the ESP Ghostscript component in ordr to be able to print via CUPS.
I found this component in Gimp-Print's web page and installed it to see if that solved the problem. Apparently it did, so in fact I did not have to go all the way to install the gimp-print software. The EPS Ghostscript alone solved the problem; so far so good.