50 NL, check/raised on flop with overpair

[QuattroFour4]

Villain has check/raised me in the last two hands I've been involved in...I don't think there is any reason to believe he has a real hand here, but I may be wrong.

PokerStars No-Limit Hold'em, $0.50 BB (6 handed) Hand History Converter Tool from FlopTurnRiver.com (Format: 2+2 Forums)

Button ($5.70)
SB : Villain ($64.35)
BB ($17.25)
Hero ($53)
MP ($61.85)
CO ($84.10)

Preflop: Hero is UTG with A[img]/images/graemlins/diamond.gif[/img], A[img]/images/graemlins/heart.gif[/img].
<font color="#CC3333">Hero raises to $2</font>, <font color="#666666">3 folds</font>, SB : Villain calls $1.75, <font color="#666666">1 fold</font>.

Flop: ($4.50) 6[img]/images/graemlins/heart.gif[/img], 5[img]/images/graemlins/club.gif[/img], 3[img]/images/graemlins/club.gif[/img] <font color="#0000FF">(2 players)</font>
Villain checks, <font color="#CC3333">Hero bets $2.5</font>, <font color="#CC3333">Villain raises to $10</font>, <font color="#CC3333">Hero?