Ahh, sh*t. I feel your pain. I hate people who can check twice with very good hands.
That said, I think at the river you have a case of every-hand-that-calls-you-beats-you. It's tempting to bet it with the other guy's two checks looking so weak, but you gotta resist that temptation.
You said you were done with the hand, and then ten seconds later you're betting. I do that all the time. Definite leak. Yuck.