AA facing deep flop push

[Dave I]

This is about my 4th orbit. Have not seen much out of villain except he is passive pre-flop and very aggressive post-flop. I very seriously doubt he has two pair here. So, does he have a set? If so, why try to push me out. This is a pretty dry flop. Does anyone think this a clear call or clear fold?

Absolute Poker
No Limit Holdem Ring game
Blinds: $0.10/$0.25
5 players
Converter

Stack sizes:
Dave: $59.70
CO: $4
Button: $27.45
SB: $28.95
BB: $55.85

Pre-flop: (5 players) Dave is UTG with A[img]/images/graemlins/heart.gif[/img] A[img]/images/graemlins/spade.gif[/img]
<font color="#cc3333">Dave raises to $1.5</font>, CO calls $1.5, 2 folds, BB calls $1.25.

Flop: 9[img]/images/graemlins/diamond.gif[/img] 3[img]/images/graemlins/club.gif[/img] Q[img]/images/graemlins/spade.gif[/img] ($4.6, 3 players)
BB checks, <font color="#cc3333">Dave bets $4</font>, <font color="#cc3333">CO 2.5 $2.5</font>, <font color="#cc3333">BB raises all-in $54.35</font>, Dave ??