another big fold

[sh58]

Party Poker, $1/$2 NL Hold'em Cash Game, 6 Players
LeggoPoker.com - Hand History Converter

BB: $175.10
sh58 (UTG): $290.15
MP: $230.17
CO: $54.15
BTN: $405.30
SB: $318.15

Pre-Flop: A[img]/images/graemlins/heart.gif[/img] Q[img]/images/graemlins/spade.gif[/img] dealt to sh58 (UTG)
<font color="red">sh58 raises to $8</font>, 3 folds, SB calls $7, BB calls $6

Flop: ($24) Q A[img]/images/graemlins/spade.gif[/img] 6[img]/images/graemlins/heart.gif[/img] (3 Players)
SB checks, BB checks, <font color="red">sh58 bets $18</font>, SB calls $18, BB folds

Turn: ($60) 9 (2 Players)
SB checks, <font color="red">sh58 bets $45</font>, <font color="red">SB raises to $90</font>, sh58 calls $45

River: ($240) 5 (2 Players)
<font color="red">SB bets $200</font>, sh58 folds


yuck yuck yuck yuck

villain is massive nit 16/5/1.5. no history although i have been pretty aggro so far

the thought crossed my mind that he may flat with AK and maybe overvalue it like this, but then i thought in that case he may also flat with AA or QQ.

what a nit i am... anyone else fold here?