Fold two pair on the river?

[xenthebrain]

Should I have check/called the river instead?
I tried the value bet, but as he raised I was sure he had either the straight or the flush.
My thinking was, that he would have raised the turn instead if he was bluffing, but whenever I find my self calling such river raises I'm toast.

Party Poker 0.5/1 Hold'em (10 handed) converter

Preflop: Hero is BB with 5[img]/images/graemlins/heart.gif[/img], 7[img]/images/graemlins/club.gif[/img]. MP1 posts a blind of $0.5.
<font color="#666666">3 folds</font>, MP1 (poster) checks, MP2 calls, <font color="#666666">3 folds</font>, SB completes, Hero checks.

Flop: (4 SB) 5[img]/images/graemlins/spade.gif[/img], 7[img]/images/graemlins/diamond.gif[/img], 3[img]/images/graemlins/diamond.gif[/img] <font color="#0000FF">(4 players)</font>
SB checks, <font color="#CC3333">Hero bets</font>, MP1 folds, MP2 calls, SB folds.

Turn: (3 BB) 4[img]/images/graemlins/diamond.gif[/img] <font color="#0000FF">(2 players)</font>
<font color="#CC3333">Hero bets</font>, MP2 calls.

River: (5 BB) K[img]/images/graemlins/spade.gif[/img] <font color="#0000FF">(2 players)</font>
<font color="#CC3333">Hero bets</font>, <font color="#CC3333">MP2 raises</font>, Hero folds.

Final Pot: 8 BB