I restarted the PC again this morning, and yet again, tried to log into the DSL.
I did the SAME freakin' things I was trying to do last night, and this time it logged in immediately.
I have no clue why the Gremlins were afoot last night, but not today. But I'm certainly not complaining. Now that the PC is back online, that's one less dose of TUMS I'll have to take.