A clue about inbound port forwarding?

I ran out of ideas for things to check a long time ago with my problems with inbound port forwarding but I just had something happen that might provide a clue. (I'm assuming you've read that other post about the problem so I won't repeat the pertinent details here.)

I do most of my browsing in Opera, of course, but I keep IE around for those very few sites that need it. One of them is, unfortunately, HomeSeer's primary interface; thus, my IE home page is set to http://tricklebrook.dyndns.org:81/ as that's the main place I go with it. Thanks to the Linksys's router, even though that maps to my network's external address 70.41.162.55 (at the moment), even from inside it gets directed through the port forwarding to the right place.

IE is also the only way to access Windows Update, which I typically do from work. Thus, I start up IE and it tries to go to my HomeSeer site, fails, and I click Windows Update and it goes on from there. Done this dozens of times since the inbound port forwarding problem showed up and it went the same way each time.

Except today, it popped up the login credentials box to access HomeSeer, with the user ID and password already filled in. Excitedly, I clicked OK, and then... got the blank "The page cannot be displayed" page after all.

How could it be getting in at all, and then failing? One would wonder if the problem is in HomeSeer, thought it's hard to see how; but if it were, why would the same problem affect using SSH to get into my Linux box in the basement? Also, why would it be affecting attempts to access it using Opera just the same?

Attempts to repeat this odd little incident failed; it's back to the usual behavior of not loading at all. Maybe it doesn't mean anything.