30/60 SB vs BB

[helpmeout]

I normally dont play the 30/60 nor shorthand but a decent provider was there.

Opponent is a solid player fairly aggressive had been raising me HU about 3 times after I have limped in from SB.

I decided to take a stand and play slightly more aggressive.

I hadn't played overly aggressive postflop or from SB. So I expected him to fold a low PP to my river bet.

Party Poker 30/60 Hold'em (4 handed) converter (http://www.selachian.com/tools/bisonconverter/hhconverter.cgi)

Preflop: Hero is SB with 2/images/graemlins/spade.gif, 2/images/graemlins/club.gif.
<font color="#666666">2 folds</font>, <font color="#CC3333">Hero raises</font>, <font color="#CC3333">BB 3-bets</font>, <font color="#CC3333">Hero caps</font>, BB calls.

Flop: (8 SB) 3/images/graemlins/diamond.gif, Q/images/graemlins/club.gif, T/images/graemlins/club.gif <font color="#0000FF">(2 players)</font>
<font color="#CC3333">Hero bets</font>, <font color="#CC3333">BB raises</font>, <font color="#CC3333">Hero 3-bets</font>, BB calls.

Turn: (7 BB) Q/images/graemlins/diamond.gif <font color="#0000FF">(2 players)</font>
<font color="#CC3333">Hero bets</font>, BB calls.

River: (9 BB) 4/images/graemlins/spade.gif <font color="#0000FF">(2 players)</font>
<font color="#CC3333">Hero bets</font>

[donger]

[ QUOTE ]
I hadn't played overly aggressive postflop or from SB. So I expected him to fold a low PP to my river bet.

[/ QUOTE ]

Why would he call the turn and then fold the river? The river was a total blank.