Live $1/$2 NL: Bottom Set v. Aggressive Betting

[KipBond]

Live $1/$2 NL - ~$250 Stacks

Pre-Flop: UTG is a semi-tight, aggressive, strong player. UTG limps <font color="blue">(very rare)</font>. MP limps. I'm on the button with 4[img]/images/graemlins/club.gif[/img] 4[img]/images/graemlins/diamond.gif[/img] I limp. SB folds. BB checks.

Flop ($9 - $1 rake): Q[img]/images/graemlins/club.gif[/img] 8[img]/images/graemlins/club.gif[/img] 4[img]/images/graemlins/heart.gif[/img]

UTG bets $10. MP folds. I pause, then call. BB folds.
<font color="blue">I would normally raise someone here, but UTG is a good player. His marginal over-sized pot bet leads me to believe he has a weak Q. I want him to think I'm on a flush draw.</font>

Turn ($30 - $3 rake): 7[img]/images/graemlins/club.gif[/img]

UTG bets $25. I call.
<font color="blue">Maybe he didn't put me on a flush draw? Why is he betting so much? Is this set over set? I'm confused.</font>

River ($80 - $5 rake): 2[img]/images/graemlins/diamond.gif[/img]

UTG bets $50

What do I do?? Please analyze my thoughts on the flop. What should I have been thinking on the turn?