[Andy B]

I think that fourth is still a fold. Given the cards that are out, he can have:

Trip Queens--37 ways
Aces-up--1 way
Kings-up--6 ways
Queens and Jacks--6 ways
Queens and Tens--3 ways

You're losing to all of these, and the trips have you crushed. For him to have something else, he would have to have raised first-in with a three-flush with two diamonds gone or something like KQJ with a Ten and a Nine gone. If the other guy is a maniac, sure, continue, but mention that in the original post.

Checking the river might be common, but betting is better.