Update:
I downloaded Thunderbird and will try a reinstall this weekend if the POP still doesn't work tomorrow.
In the meantime, I created a temporary account using the resident Windows mail program using the same information I used on Thunderbird...just let it auto create as an IMAP rather than using Manual to make the new account a POP.
It worked like a dream.
So the problem has to do with Thunderbird and since it happened within the last 24 hours it must be that either Thunderbird is having issues, The HP update corrupted the Thunderbird, or the Windows Optional before last did.
In any case, I found the window that lists all my Windows Update downloads including up to today's....but there doesn't appear to be a way to uninstall the MSE definitions updates (the only Optionals that have been downloaded.) This doesn't make sense. Why would only Important updates allow the computer owner to uninstall them?

Checked HP's help site and couldn't find any list of recent updates from them either. No idea if it was a driver update or what they sent me. Tomorrow I'm also going to try to find how to turn off the b-danged auto updater so I can at least take a look at descriptions before an update gets installed!