I went back and forth for a little on this. The preflop 3-bet followed by the flop check is unnerving. It could be that he has AK/AQ and doesn't auto-bet the flop with high cards, or he could have AA/KK/TT and is getting cute with it (though I don't think he's getting cute with AA/KK too often). Even if my bet is raised by LAG, I don't know if I expect SB to fold on the flop if he has AK (maybe with AQ).
Betting to get rid of LAG button (if he had nothing) wouldn't be so bad, but I decided to check, half-way hoping that LAG would take the initiative and bet it for me so I could see what SB would do. If SB check-raised, I would be gone without investing any more than I needed to. If SB check-called, I'd call behind and see what happens on the turn (putting SB on overcards most of the time, but still keeping an eye out for slowplaying silliness). And if it got checked through, I think it's okay because I probably don't have the best hand anyway. I'm not sold that checking is better than betting, but I'm not sure if there's enough value in betting to fire away (probably) without the best hand. I don't know if I can run villlain off of AK, and this information would have been very helpful in the decision-making process.
Paradise Poker 1/2 Hold'em (4 handed)
FTR converter on zerodivide.cx
Preflop: Hero is UTG with J[img]/images/graemlins/club.gif[/img], A[img]/images/graemlins/diamond.gif[/img].
<font color="#CC3333">Hero raises</font>, Button calls, <font color="#CC3333">SB 3-bets</font>, <font color="#666666">
1 fold</font>, Hero calls, Button calls.
Flop: (10 SB) 2[img]/images/graemlins/club.gif[/img], 3[img]/images/graemlins/club.gif[/img], T[img]/images/graemlins/diamond.gif[/img] <font color="#0000FF">(3 players)</font>
SB checks, Hero checks, <font color="#CC3333">Button bets</font>, SB calls, Hero calls.
Turn: (6.50 BB) 3[img]/images/graemlins/heart.gif[/img] <font color="#0000FF">(3 players)</font>
SB checks, Hero ...