What is going on here? Odd turn action.

[Schizo]

SB = 20/8/1.33 over 80 hands
no read on MP3


Party Poker 3/6 Hold'em (10 handed) converter

Preflop: Hero is MP1 with 9[img]/images/graemlins/club.gif[/img], 9[img]/images/graemlins/heart.gif[/img]. MP3 posts a blind of $3.
UTG calls, <font color="#666666">2 folds</font>, Hero calls, <font color="#666666">1 fold</font>, MP3 (poster) checks, CO calls, Button calls, <font color="#CC3333">SB raises</font>, <font color="#666666">1 fold</font>, UTG calls, Hero calls, MP3 calls, CO calls, Button calls.

Flop: (13 SB) 2[img]/images/graemlins/heart.gif[/img], 5[img]/images/graemlins/spade.gif[/img], 8[img]/images/graemlins/diamond.gif[/img] <font color="#0000FF">(6 players)</font>
SB checks, UTG checks, <font color="#CC3333">Hero bets</font>, MP3 calls, CO calls, Button calls, <font color="#CC3333">SB raises</font>, UTG folds, Hero calls, MP3 calls, CO calls, Button calls.

Turn: (11.50 BB) A[img]/images/graemlins/club.gif[/img] <font color="#0000FF">(5 players)</font>
SB checks, Hero checks, MP3 checks, CO checks, Button checks.

River: (11.50 BB) 6[img]/images/graemlins/spade.gif[/img] <font color="#0000FF">(5 players)</font>
SB checks, Hero checks, <font color="#CC3333">MP3 bets</font>, CO folds, Button folds, SB calls, Hero ....?

Normally I would fold this without a thought, but the turn and river play are puzzling.