On my second Dell machine Dimension xps R450. I think I found out why Cups could not detect my LPT (parallel Printer). In The BIOS, Under ADVANCED tab on this machine, first option is PLUG AND PLAY O/S. I had YES, but I changed it to NO. Rebooted, and then was able to see LPT#1 when I opened CUPS. After that it was a breeze, I printed a test page. My conclusion is linux is not a plug and play operating system. And I could be wrong, so someone correct me please.
Good detective worki! I've read in numerous places that if your BIOS offers the Plug and Play OS option, you should choose NO if you're going to install Linux. Windows works fine with NO. I've been choosing NO for several years on several computers and I didn't think of it as a possible solution to your problems.
Let us know how things go from this point on.