$55: Have TPTK and facing a reraise on flop

[AA suited]

PartyPoker, Big Blind is t50 (7 handed) Converter on pregopoker.com

UTG (t1675)
UTG+1 (t1065)
MP1 (t1310)
CO (t1685)
Button (t2005)
HERO (t1455)
BB (t805)

Preflop: HERO is in SB with A[img]/images/graemlins/club.gif[/img] K[img]/images/graemlins/spade.gif[/img]
<font color="red">UTG raises t100</font>, UTG+1 calls t100, <font color="gray">MP1 folds</font>, <font color="gray">CO folds</font>, <font color="gray">Button folds</font>, HERO calls t75, <font color="gray">BB folds</font>

Flop: (t350) 9[img]/images/graemlins/club.gif[/img] 7[img]/images/graemlins/heart.gif[/img] K[img]/images/graemlins/heart.gif[/img] (3 players)
HERO checks, <font color="red">UTG bets t200</font>, <font color="gray">UTG+1 folds</font>, <font color="red">HERO raises t400</font>, <font color="red">UTG raises t400</font>, HERO? [img]/images/graemlins/confused.gif[/img]

no reads. UTG's min raise preflop could mean anything.

What would you do, and why?