Hey All,
1) Thanks for all your input and advise. As always, I really appreciate the combined expertise of the forum.
2) Did you know that, even though DC fuses are designed to blow apart so that you can visually see the break in the plastic window, sometimes they don't?
Here's what happened:
After checking all the fuses and connections, finding nothing and then posting, I pulled the furnace out of the cabinet to check wiring, etc. Nothing wrong there. I went through the vendor documentation for troubleshooting and nothing seemed to fit.
I then took my multi-meter and retested the fuses -- and the furnace fuse was faulty! Not blown through mind you so that you could see it. The filament was cracked so it kind of made a connection, but not reliably. When I bent the fuse just a little bit, it would show as open (blown) in the meter. But when I just checked it as it lay on the bench, sometimes it read fine.
So I replaced the stupid fuse and everything runs fine now.
And it only took me eight hours. :(