Top set facing shuv on straight board?

[Xexilla]

again player has only just sat down... is this an easy pass is he ever just doing this with 2 pair or a lower set?? or a stone cold bluff?? I think I shud fold but I just have trouble believing anyone would play a straight like this as im insta mucking a hand like Aces.

Poker Stars, $0.25/$0.50 NL Hold'em Cash Game, 6 Players
LeggoPoker Hand History Converter

BTN: $17.15
SB: $19.85
BB: $53.40
Hero (UTG): $80.05
MP: $48.50
CO: $44.60

Pre-Flop: 8[img]/images/graemlins/heart.gif[/img] 8[img]/images/graemlins/spade.gif[/img] dealt to Hero (UTG)
<font color="red">Hero raises to $2</font>, 3 folds, SB calls $1.75, BB calls $1.50

Flop: ($6) 7[img]/images/graemlins/diamond.gif[/img] 4[img]/images/graemlins/club.gif[/img] 5[img]/images/graemlins/heart.gif[/img] (3 Players)
SB checks, <font color="red">BB bets $2</font>, <font color="red">Hero raises to $7</font>, SB folds, BB calls $5

Turn: ($20) 8[img]/images/graemlins/club.gif[/img] (2 Players)
<font color="red">BB bets $44.40 and is All-In</font>

Results: $20 Pot ($20 Rake)