Call down or fold?

BB is unknown and has just sat down at table for like 10 hands. Nothing to indicate maniac so far. Call down or fold?

Party Poker 3/6 Hold'em (6 max, 6 handed) FTR converter on zerodivide.cx

Preflop: Hero is MP with A[img]/images/graemlins/diamond.gif[/img], 9[img]/images/graemlins/spade.gif[/img].
<font color="#666666">1 fold</font>, <font color="#CC3333">Hero raises</font>, <font color="#666666">1 fold</font>, Button calls, SB calls, BB calls.

Flop: (8 SB) 2[img]/images/graemlins/heart.gif[/img], 9[img]/images/graemlins/diamond.gif[/img], 7[img]/images/graemlins/heart.gif[/img] <font color="#0000FF">(4 players)</font>
<font color="#CC3333">SB bets</font>, BB calls, <font color="#CC3333">Hero raises</font>, Button folds, SB calls, BB calls.

Turn: (7 BB) 7[img]/images/graemlins/spade.gif[/img] <font color="#0000FF">(3 players)</font>
SB checks, BB checks, <font color="#CC3333">Hero bets</font>, SB calls, <font color="#CC3333">BB raises</font>, Hero ???