Too slow?

[msb]

I think I played this too slow... but I had the board absolutely crippled. I'd like to hear comments, even though this is a pretty rare case.

Party Poker No-Limit Hold'em, $ BB (9 handed) converter

SB ($51.10)
BB ($45.25)
UTG ($45.45)
Hero ($50)
MP1 ($101.37)
MP2 ($52.50)
MP3 ($50)
CO ($52.95)
Button ($58.80)

Preflop: Hero is UTG+1 with K[img]/images/graemlins/club.gif[/img], J[img]/images/graemlins/diamond.gif[/img]. SB posts a blind of $0.25.
<font color="#666666">1 fold</font>, Hero calls $0.50, <font color="#666666">2 folds</font>, MP3 calls $0.50, <font color="#666666">3 folds</font>, BB checks.

Flop: ($1.75) K[img]/images/graemlins/diamond.gif[/img], K[img]/images/graemlins/spade.gif[/img], J[img]/images/graemlins/spade.gif[/img] <font color="#0000FF">(3 players)</font>
BB checks, Hero checks, <font color="#CC3333">MP3 bets $1</font>, BB folds, Hero calls $1.

At this point I have the board crippled and I'm praying someone's got the case King or a spade draw. Anyway, no harm in smooth calling here, right?

Turn: ($3.75) A[img]/images/graemlins/club.gif[/img] <font color="#0000FF">(2 players)</font>
Hero checks, <font color="#CC3333">MP3 bets $1</font>, Hero calls $1.

I don't have the nuts anymore, but I don't have him on AA or AK, so I figure this might be a decent card for me. I was planning on check-raising, but the small bet leads me to believe he's on a draw, so I just call to give him a chance to catch.

River: ($5.75) A[img]/images/graemlins/diamond.gif[/img] <font color="#0000FF">(2 players)</font>

Oops. Now what?

Hero ?