99 vs. 4 Flush on the Board

[srt19170]

Party Poker 0.5/1 Hold'em (9 handed)

Preflop: Hero is MP1 with 9[img]/images/graemlins/diamond.gif[/img], 9[img]/images/graemlins/heart.gif[/img].
UTG calls, <font color="666666">1 fold</font>, <font color="CC3333">Hero raises</font>, MP2 calls, <font color="666666">3 folds</font>, SB calls, <font color="666666">1 fold</font>, UTG calls.

Flop: (9 SB) 7[img]/images/graemlins/spade.gif[/img], 8[img]/images/graemlins/club.gif[/img], 4[img]/images/graemlins/club.gif[/img] <font color="blue">(4 players)</font>
SB checks, UTG checks, <font color="CC3333">Hero bets</font>, MP2 calls, SB calls, UTG folds.

Turn: (6 BB) 3[img]/images/graemlins/club.gif[/img] <font color="blue">(3 players)</font>
SB checks, <font color="CC3333">Hero bets</font>, MP2 folds, SB calls.

I think it's all pretty standard up to here. I'm betting here just for value; if MP2 or SB are after the runner-runner flush draw, they've got the odds regardless.

River: (8 BB) J[img]/images/graemlins/club.gif[/img] <font color="blue">(2 players)</font>
<font color="CC3333">SB bets</font>, Hero calls.

Do you call this bet? I'm fairly certain SB has hit his flush when he comes out betting. Probably not his only value (maybe he had middle pair or something) but he's probably hit his flush. He's offering me 9:1... Should I call? Do you think I'm good 10% of the time?

-- Scott