Go broke in a limped pot???

[Vinny80]

Villain is tag 17/15/5. We've had a few battles, mostly preflop, but no big pot to showdown yet today. He's a good player and he's not splashing chips around too much, but he's very aggro postflop. I have a hard time beleiving this is anything but a full house, but can I fold???

Cryptologic - No Limit Hold'em Cash Game - $2/$5 Blinds - 6 Players - (LegoPoker Hand History Converter)

SB: $950.10
Hero (BB): $757.05
UTG: $679.57
MP: $575.41
CO: $665.85
BTN: $493.00

Preflop: Hero is dealt 3[img]/images/graemlins/diamond.gif[/img] K[img]/images/graemlins/diamond.gif[/img] (6 Players)
UTG calls $5.00, MP calls $5.00, 2 folds, SB calls $3.00, Hero checks

Flop: ($20) 5[img]/images/graemlins/diamond.gif[/img] 2[img]/images/graemlins/diamond.gif[/img] 6[img]/images/graemlins/club.gif[/img] (4 Players)
<font color="red">SB bets $15.00</font>, <font color="red">Hero raises to $45.00</font>, 2 folds, SB calls $30.00

Turn: ($110) A[img]/images/graemlins/diamond.gif[/img] (2 Players)
SB checks, <font color="red">Hero bets $90.00</font>, SB calls $90.00

River: ($290) 6[img]/images/graemlins/heart.gif[/img] (2 Players)
<font color="red">SB bets $200.00</font>, [i]Hero