Critical pots

I seem to keep losing critical pots at the moment. Had I won this, I'd have been certain to make the money. If I'd have been in Duke's position, I'd have never called with a weak ace. With this move, I was hoping to steal the blinds.

Game #2447083334: Hold'em NL (200/400) - 2006/05/21 - 16:02:57 (GMT)
Table "STT1 2654724 - 1" Seat 6 is the button.
Seat 1: bongo (874 in chips)
Seat 3: Devochka (2020 in chips)
Seat 6: RumTiddle (1515 in chips)
Seat 7: Raoulduke (1562 in chips)
Seat 8: Angel5000 (4029 in chips)
Raoulduke: posts small blind 200
Angel5000: posts big blind 400
----- HOLE CARDS -----
dealt to RumTiddle [9d Ah]
bongo: folds
Devochka: folds
RumTiddle: raises to 1515 and is all-in
Raoulduke: raises to 1562 and is all-in
Angel5000: folds
Returned uncalled bets 47 to Raoulduke
----- FLOP ----- [2s As Kd]
----- TURN ----- [2s As Kd][4s]
----- RIVER ----- [2s As Kd 4s][5d]
----- SHOW DOWN -----
Raoulduke: shows [4c Ac] (Two Pairs, Aces and Fours, King high)
RumTiddle: shows [9d Ah] (A Pair of Aces, King high)
Raoulduke collects 3430 from Main pot
----- SUMMARY -----
Total pot 3430 Main pot 3430 Rake 0
Board [2s As Kd 4s 5d]
Seat 1: bongo folded before Flop (didn't bet)
Seat 3: Devochka folded before Flop (didn't bet)
Seat 6: RumTiddle (button) showed [9d Ah] and lost
Seat 7: Raoulduke (small blind) showed [4c Ac] and won (3430) with Two Pairs, Aces and Fours, King high
Seat 8: Angel5000 (big blind) folded before Flop (didn't bet)