$11- River Straight In Trouble

[kevkev60614]

PokerStars No-Limit Hold'em Tourney, Big Blind is t50 (6 handed) converter

CO (t5000)
Button (t1810)
SB (t2115)
Hero (t1230)
UTG (t1350)
MP (t1995)

Preflop: Hero is BB with 9[img]/images/graemlins/diamond.gif[/img], 7[img]/images/graemlins/club.gif[/img].
<font color="#666666">1 fold</font>, MP calls t50, <font color="#666666">2 folds</font>, SB completes, Hero checks.

Flop: (t150) 8[img]/images/graemlins/heart.gif[/img], K[img]/images/graemlins/spade.gif[/img], 6[img]/images/graemlins/spade.gif[/img] <font color="#0000FF">(3 players)</font>
<font color="#CC3333">SB bets t100</font>, Hero calls t100, MP calls t100.

Turn: (t450) A[img]/images/graemlins/diamond.gif[/img] <font color="#0000FF">(3 players)</font>
SB checks, Hero checks, MP checks.

River: (t450) T[img]/images/graemlins/spade.gif[/img] <font color="#0000FF">(3 players)</font>
<font color="#CC3333">SB bets t100</font>, Hero calls t100, <font color="#CC3333">MP raises to t500</font>, SB folds, Hero...

Both MP and SB have been pretty tight thus far. So how badly was this played, and where do I go from here?