5/10: Weird hand I iso raise QT hit an iffy river

[imported_leader]

CO has been tight passivish in his first 18 hands. So basically assume he's not a manic.
MP is 30/20ish TAG over a small sample.

PokerStars 5/10 Hold'em (6 handed) FTR converter on zerodivide.cx

Preflop: Hero is Button with T[img]/images/graemlins/heart.gif[/img], Q[img]/images/graemlins/spade.gif[/img].
<font color="#666666">2 folds</font>, CO calls, <font color="#CC3333">Hero raises</font>, <font color="#CC3333">SB 3-bets</font>, <font color="#666666">1 fold</font>, CO calls, Hero calls.

Not much of a read on CO so I go for the iso raise. Bad? BB is tight.

Flop: (10 SB) 5[img]/images/graemlins/heart.gif[/img], 6[img]/images/graemlins/spade.gif[/img], A[img]/images/graemlins/spade.gif[/img] <font color="#0000FF">(3 players)</font>
SB checks, CO checks, Hero checks.

umm WTF? I checked because I'm beat like always and didn't think people were folding.

Turn: (5 BB) 7[img]/images/graemlins/spade.gif[/img] <font color="#0000FF">(3 players)</font>
SB checks, <font color="#CC3333">CO bets</font>, Hero calls, SB calls.

River: (8 BB) T[img]/images/graemlins/club.gif[/img] <font color="#0000FF">(3 players)</font>
SB checks, <font color="#CC3333">CO bets</font>, Hero...

I'm leaning toward fold. Weak?