Give him credit for an overpair?

[Matador225]

Hand from earlier today in the Party for Free $100,000

Villain seemed to be pretty solid and had only shown down strong hands since I had been at the table. Also his standard raise was what he raised to in this hand.

#Game No : 3224490806
***** Hand History for Game 3224490806 *****
NL Texas Hold'em Trny:18397682 Level:5 Blinds (50/100) - Sunday, December 18, 20:18:23 EDT 2005
Table Party for Free $100,000(527145) Table #67 (Real Money)
Seat 10 is the button
Total number of players : 10
Seat 2: NJKowboy22 ( $2540 )
Seat 3: mangy71 ( $1905 )
Seat 4: YDNEW ( $945 )
Seat 6: Mr_Insidious ( $2860 )
Seat 7: Normandy44 ( $4480 )
Seat 9: stanforth ( $265 )
Seat 10: snowman052 ( $4350 )
Seat 8: Runningtowin ( $6592 )
Seat 5: phillydogg19 ( $1870 )
Seat 1: LooseOos ( $3432 )
Trny:18397682 Level:5
Blinds (50/100)
** Dealing down cards **
Dealt to NJKowboy22 [ 9s 9d ]
mangy71 folds.
YDNEW folds.
phillydogg19 folds.
Mr_Insidious raises [225].
Normandy44: Why?
Normandy44 folds.
Runningtowin folds.
stanforth folds.
snowman052 folds.
LooseOos calls [175].
NJKowboy22 calls [125].
** Dealing Flop ** [ 7d, 8h, 3h ]
LooseOos checks.
NJKowboy22 bets [400].
Mr_Insidious is all-In [2635]
LooseOos folds.

I don't generally make this fold with no reads but villain's line left me thinking I was behind. What is everyone's default play here given this line against a fairly tight and solid player?

Thanks a lot,
Jack