Another Min Raise: Straight on a flush board

[beset7]

Villain is 59/10/3. His aggression factor on the river is 6 (!?!).

These situations never fail me to trip me up. Whats your line. I think I fold to many winners here and push to many losers. Any input, standard lines, suggestions would be appreciated. Thanks.

PokerStars No-Limit Hold'em, $1.00 BB (5 handed) converter

Hero ($99.50)
MP ($108)
Button ($101)
SB ($17.05)
BB ($31.90)

Preflop: Hero is UTG with 9[img]/images/graemlins/diamond.gif[/img], 8[img]/images/graemlins/diamond.gif[/img].
Hero calls $1, <font color="#666666">1 fold</font>, Button calls $1, <font color="#666666">1 fold</font>, BB checks.

Flop: ($3.50) Q[img]/images/graemlins/club.gif[/img], T[img]/images/graemlins/club.gif[/img], 6[img]/images/graemlins/heart.gif[/img] <font color="#0000FF">(3 players)</font>
BB checks, <font color="#CC3333">Hero bets $3</font>, Button calls $3, BB folds.

Turn: ($9.50) 7[img]/images/graemlins/club.gif[/img] <font color="#0000FF">(2 players)</font>
Hero bets $9, Button raises to $18, Hero...