HUSNG: Villain pushes river after checking down

[ghettointlectual]

So this villain had been pretty passive the first part of the match, as soon as he gets to less than 1000 in chips and the blinds go up he starts playing back at me. In several hands before this one villain has been 3betting my pf raises all in and I have folded. Given recent history is this a bluff enough of the time for me to call. By enough I mean a 55-60% of the time.
Full Tilt Poker
No Limit Holdem Tournament
Blinds: t20/t40
2 players
Converter

Stack sizes:
Hero: t2025
BB: t975

Pre-flop: (2 players) Hero is SB with A[img]/images/graemlins/club.gif[/img] 4[img]/images/graemlins/heart.gif[/img]
<font color="#cc0000">Hero raises to t80</font>, BB calls t40 <font color="aaaaaa">(pot was t100)</font>.

Flop: 9[img]/images/graemlins/heart.gif[/img] 6[img]/images/graemlins/spade.gif[/img] 5[img]/images/graemlins/spade.gif[/img] (t160, 2 players)
BB checks, Hero checks.

Turn: 6[img]/images/graemlins/club.gif[/img] (t160, 2 players)
BB checks, Hero checks.

River: A[img]/images/graemlins/diamond.gif[/img] (t160, 2 players)
<font color="#cc0000">BB is all-in t895</font>. Hero ??

[soop]

You raised preflop/he just calls. Then he decides to open push only after the ace hits. He is pretty much always value betting something that beats an ace. There are plenty of possibilities on that board.