200BB deep, bottom set, ugly action

[Dex]

Absolute Poker
No Limit Holdem Ring game
Blinds: $0.25/$0.50
5 players
Converter

Stack sizes:
Hero: $134.42
CO: $63.55
Button: $106.65
SB: $99.50
BB: $34.80

Nothing goofy has happened at this table yet and I'm multitabling so no strong reads. Button seemed to have been playing fairly LAGgy although I hadn't noticed anything too out-of-line.

Pre-flop: (5 players) Hero is UTG with 3[img]/images/graemlins/club.gif[/img] 3[img]/images/graemlins/heart.gif[/img]
Hero calls, CO calls, <font color="#cc0000">Button raises to $1</font>, SB folds, BB calls, Hero calls, CO calls.

Flop: 3[img]/images/graemlins/spade.gif[/img] 7[img]/images/graemlins/spade.gif[/img] 4[img]/images/graemlins/heart.gif[/img] ($4.25, 4 players)
BB checks, Hero checks ...

Normally I'd bet here, but I had bet my last two flopped sets at this table into the PFR and everyone folded. So I decided to check and let Button do his thing.

... <font color="#cc0000">CO bets $0.5</font>, <font color="#cc0000">Button raises to $3</font>, <font color="#cc0000">BB raises to $6</font>, Hero ... ?