nl25 tricky spot with middle pair

[mop06]

Villain is a solid regular. How's the check-raise on the flop? Action on the river?

Full Tilt Poker - No Limit Hold'em Cash Game - $0.10/$0.25 Blinds - 6 Players - (LegoPoker HH Converter (http://www.legopoker.com/hh))

Hero (SB): $36.65
BB: $35.25
UTG: $57.55
MP: $11.45
CO: $26.15
BTN: $24.65

Preflop: Hero is dealt 8/images/graemlins/club.gif 8/images/graemlins/diamond.gif (6 Players)
2 folds, CO raises to $0.85, BTN folds, Hero calls $0.75, BB folds

Flop: ($1.95) Q/images/graemlins/heart.gif 7/images/graemlins/diamond.gif 7/images/graemlins/spade.gif (2 Players)
Hero checks, CO bets $1.35, Hero raises to $3.50, CO calls $2.15

Turn: ($8.95) 3/images/graemlins/spade.gif (2 Players)
Hero checks, CO checks

River: ($8.95) 4/images/graemlins/heart.gif (2 Players)
Hero checks, CO bets $3.00, Hero ???

[goat_beard]

looks like a value bet from villian. i cant see air here as part of his range. maybe just maybe a whiffed AK.