(Gee, I almost found myself saying "issues" in the post header. Don't you hate the new use of "issue" to mean "problem"?)
The connectivity problems referred to in the title are not to this site. As you can see, here I am. Ta-da! I also have e-mail and can connect to nearly all of my usual Internet sites. However, I suddenly (as of yesterday morning) cannot connect to my beloved group blog, to which I am a contributor, What's Wrong With the World.
By asking all my friends to try it and see if they can connect, I have narrowed down the problem to, apparently, my own house. My neighbor across the street has the same ISP that I do, and he can get the site.
I found this nifty article that may diagnose the problem. If so, we'll have to call in an expert. (I hope our physically local expert is available; he isn't always.) It says "only experienced Windows-savvy users" should attempt the workaround described, so I think we'll probably not try it ourselves. If this should turn out to be the problem, the mystery is why it suddenly arose yesterday morning, when nothing had changed in our local configuration.
Anyway, to all my many fans, I will be able to blog only here for a while, not at WWWtW, until it's all back up and running. One always hopes, with a trace of superstition, that the problem will just "fix itself." Maybe I'll wake up again tomorrow and it will all be better. Evidently (according to the article) that could actually happen if various servers started sending smaller "packets" that could fit down the "tunnel" of my router. Or something.
Update: The problem appears to be our local wireless router. When we plug the cable modem directly into the computer I use, the problem goes away. All sites become available. Unfortunately this means that no one else can use the Internet from a laptop at the same time. So for the time being, the cludge is that when no one else needs to use the Internet, I can switch the cables, reboot the computer (it doesn't work otherwise), and then go wherever I want on the Internet. When the wireless router is needed, we switch the cables back. Then I can come here, do e-mail, go most places, but not go to a few sites, including What's Wrong with the World. That's until we get an expert out here to find a better workaround. All most odd. I have a feeling some Bright Lad changed a packet size setting somewhere out there in cyberspace overnight between Friday and Saturday.
Update #2: Problem solved. The connection problem was indeed, as the article I linked above suggests, fixed by changing the MTU setting on my Linksys router down to 1492. The mystery that remains is why this should suddenly be necessary now. As far as I know, the setting has always been the factory-standard 1500, and this has never been a problem before, for over a year and a half. I've certainly never touched it before. I keep my ignorant hands off that stuff as much as possible. Anyway, thanks to Zippy and to Todd McKimmey for patient help and advice over the weekend. And thanks especially to Todd for pointing out to me what the linked article is not clear about and what I in my ignorance would have overlooked: If the problem is with the router, then the MTU setting that needs to be changed is the one on the router, not the one in the registry of the desktop computer. Of course. But it wouldn't have occurred to me. So just remember, if this esoteric problem should plague your Internet connection, the magic number is...1492.