KK Facing Reraise on Flop

[LearningCurve]

Villain was in second orbit at table and had limped in a few times. Otherwise, no real reads. What is Hero's standard play here?

PokerStars No-Limit Hold'em, $0.10 BB (9 handed) Hand History Converter Tool from FlopTurnRiver.com (Format: 2+2 Forums)

BB ($2.75)
UTG ($10.10)
UTG+1 ($7.60)
MP1 ($5.85)
MP2 ($15)
MP3 ($10.75)
CO ($24.50)
Hero ($10.15)
SB ($7.40)

Preflop: Hero is Button with K[img]/images/graemlins/club.gif[/img], K[img]/images/graemlins/diamond.gif[/img].
<font color="#666666">1 fold</font>, UTG+1 calls $0.10, MP1 calls $0.10, MP2 calls $0.10, MP3 calls $0.10, <font color="#666666">1 fold</font>, <font color="#CC3333">Hero raises to $1</font>, <font color="#666666">2 folds</font>, UTG+1 calls $0.90, MP1 folds, MP2 folds, MP3 folds.

Flop: ($2.45) 6[img]/images/graemlins/heart.gif[/img], 5[img]/images/graemlins/heart.gif[/img], 2[img]/images/graemlins/diamond.gif[/img] <font color="#0000FF">(2 players)</font>
UTG+1 checks, <font color="#CC3333">Hero bets $2</font>, <font color="#CC3333">UTG+1 raises to $4</font>, Hero...