Awkward hand means awkward river

[Bona]

PokerStars 0.25/0.50 Hold'em (8 handed) Hand History Converter Tool from FlopTurnRiver.com (Format: 2+2 Forums)

Preflop: Hero is BB with 2[img]/images/graemlins/spade.gif[/img], 6[img]/images/graemlins/spade.gif[/img]. UTG posts a blind of $0.25. MP2 posts a blind of $0.25.
UTG (poster) checks, UTG+1 calls, MP1 calls, MP2 (poster) checks, CO calls, <font color="#666666">2 folds</font>, Hero checks.

Flop: (6.40 SB) K[img]/images/graemlins/spade.gif[/img], 4[img]/images/graemlins/spade.gif[/img], 9[img]/images/graemlins/heart.gif[/img] <font color="#0000FF">(6 players)</font>
Hero checks, UTG checks, UTG+1 checks, MP1 checks, MP2 checks, <font color="#CC3333">CO bets</font>, Hero calls, UTG calls, UTG+1 calls, MP1 calls, MP2 folds.

Turn: (5.70 BB) 6[img]/images/graemlins/heart.gif[/img] <font color="#0000FF">(5 players)</font>
Hero checks, UTG checks, UTG+1 checks, MP1 checks, <font color="#CC3333">CO bets</font>, Hero calls, UTG calls, UTG+1 calls, MP1 calls.

River: (10.70 BB) T[img]/images/graemlins/spade.gif[/img] <font color="#0000FF">(5 players)</font>
Hero ?????

CO may be betting anything. He is erratic, he is 56/0/.75 after 39 hands and his passive post flop stat doesn't mean he is betting a legitimate hand. He will usually bet if checked to. The other players were new at the table. No read. No stats at the time of the hand.

What do I do with this river? Bet it and fold to a raise? Check it and c/r if CO bets when checked to? Or check call it? Or do I bet/call? I think I have a better hand than CO does but I'm afraid of the passive players, one of whom may have hit a better flush. What do you do?