AA hits a hard raise on a dry flop

[iheartponeez]

$0.1/$0.25 No Limit Holdem
6 players
Converted at weaktight.com

Stacks:
UTG (<font color="#0000cc">$14.60</font>)
UTG+1 (<font color="#0000cc">$19.40</font>)
CO (<font color="#0000cc">$10.15</font>)
BTN (<font color="#0000cc">$30.85</font>)
SB (<font color="#0000cc">$24.65</font>)
Hero (<font color="#0000cc">$27.55</font>)

Pre-flop: ($0.35, 6 players) Hero is BB A[img]/images/graemlins/diamond.gif[/img] A[img]/images/graemlins/spade.gif[/img]
UTG calls $0.25, <font color="#777777">1 fold</font>, CO calls $0.25, BTN calls $0.25, SB calls $0.15, <font color="#cc0000">Hero raises to $1.75</font>, UTG calls $1.5, <font color="#777777">CO folds</font>, BTN calls $1.5, <font color="#777777">SB folds</font>

Flop: 6[img]/images/graemlins/diamond.gif[/img] K[img]/images/graemlins/club.gif[/img] 7[img]/images/graemlins/heart.gif[/img] ($5.75, 3 players)
<font color="#cc0000">Hero bets $4</font>, <font color="#cc0000">UTG goes all-in $12.85</font>


I'm never sure which is better: Seeing someone shove on a dry flop, or on a wet flop.

On a wet flop they might be going in with draws, but they also might have a straight already.

On this flop, though, I wonder what this could be, other than a set/2-pair. Maybe AK? Is it a bad idea to fold AA when someone makes this move on a board like this?