How bad was my turn check???

[defence18]

I can't get bison's hand converter to work, so I've got to wing it.

.25/.5 NL game on Paradise Full table 10 players

UTG has $50.25, 4th has $75.00, and I have $40.50.

UTG makes it $1 to go. 2nd and 3rd fold; 4th calls.
I'm in 5th with Ad Kh and make it $3 to go.
It's folded around to UTG, who calls, as does the 4th position.
FLOP: 4s 4h 6s.

Both check to me, and I fire 6.5. UTG folds, but 4th calls.

TURN: As [4s 4h 6s]

4th checks to me as do I.

RIVER: 5h [4s 4h 6s As].

4th bets $24.

My thinking was, obviously, that he was trying to check-raise his flush on the turn, so I checked it. What do you think?

RESULTS: <font color="white"> I call $24 and he shows me 5s 5d for a full. </font>

[Big_Jim]

Turn check is fine.

River is read dependant, but you can probably fold safely against an unknown.

[Riposte]

Bet the turn. Check behind on the river.

[Big_Jim]

I suppose you're folding to c/r?

How much are you calling if he donks river?

[Riposte]

Yeah I'll let it go to a c/r. If he calls my turn bet and suddenly comes alive on the river, I'll feel like I'm pretty much beat, and probably can find a fold to half pot or more.