Problem = USB cable. I was using a crappy Radio Shack retractable thingy, and thought to myself... maybe that's the problem? (Since after all, it was whinging on about USB device not being recognized) So I switched the one I KNOW has worked, and viola. Reinstall number 324 worked just fine.
I haven't installed the 4000 on the laptop yet (the previous conflict didn't have to do with that cable, since I was using the good one for that), but plan to after I've got all my orders filled. Print, quick! Before they break again!
April - that paper-sizing problem fix was exactly as you listed! Works great now.
Shoulders and back feeling decidedly urky after sitting on the ground cussing at the install program 323 times, but otherwise in good, determined, go-get-em form.
(Oh, and Epson help is not open on weekends. Because, of course, printers don't break on weekends.)