Recently I leveled up my speech while selling to a merchant. When I finished the transaction, I got a speech choice that said "This is obviously a shakedown (persuade)." I cancelled the interaction. Now, whenever I talk to any character in the game, they all say, "Keep your voice down, do you want people to hear you? I'll let you in, just let me open the gate," and my speech levels up. So I'm leveling my speech every time I talk, but I can't talk to anyone at all! No quests, no buying or selling, just "Keep your voice down..." over and over. Does anyone know anything about this glitch?

Are you running any mods or utilities? It doesn't sound like a vanilla glitch to me..

Yes. Moonpath to Elsweyr, Space Core, and Dragon Falls Manor.

That's curious, the only time I've actually come across that line is when you try to get into Riften I think it is - and it's a guard that says it.
Have you tried reverting to a save prior to the one where it went pear-shaped?

I have saves before the problem hit. The trouble is that whenever I sell something to any merchant, my speech levels, and the problem begins anew, so basically I can't sell stuff. I wonder if setting my speech to 100 would solve the problem? It's not my favorite option, but at this point my loot is piling up.