It took me about ten seconds to decide, but I folded.
Here's the whole hand:
Party Poker 3/6 Hold'em (9 handed)
converter
Preflop: Hero is Button with A[img]/images/graemlins/heart.gif[/img], Q[img]/images/graemlins/heart.gif[/img].
<font color="#666666">
3 folds</font>, MP2 calls, <font color="#666666">
2 folds</font>, <font color="#CC3333">Hero raises</font>, <font color="#666666">
1 fold</font>, <font color="#CC3333">BB 3-bets</font>, MP2 calls, Hero calls.
Flop: (9.33 SB) T[img]/images/graemlins/diamond.gif[/img], 7[img]/images/graemlins/heart.gif[/img], K[img]/images/graemlins/spade.gif[/img] <font color="#0000FF">(3 players)</font>
<font color="#CC3333">BB bets</font>, MP2 calls, Hero calls.
Turn: (6.16 BB) T[img]/images/graemlins/heart.gif[/img] <font color="#0000FF">(3 players)</font>
BB checks, MP2 checks, Hero checks.
River: (6.16 BB) 5[img]/images/graemlins/heart.gif[/img] <font color="#0000FF">(3 players)</font>
BB checks, <font color="#CC3333">MP2 bets</font>, <font color="#CC3333">Hero raises</font>, <font color="#CC3333">BB 3-bets</font>, <font color="#CC3333">MP2 caps</font>, Hero folds, BB calls.
Final Pot: 16.16 BB
Results:
BB has Kd Kh (full house, kings full of tens).
MP2 has Tc Kc (full house, tens full of kings).
Outcome: BB wins 16.16 BB.
MP2 is much more passive than most 3/6 players, but in a trappy game like Party 3/6, I don't think BB's turn play is unusual at all. (And his numbers for the 110 hands I now have on him are 20/15/3.4.) The river check, on the other hand, did show a lot of patience.
Anyway, if he and MP2 had played faster on the turn, things could have gotten pretty uncomfortable for me on that street. I probably would have called two, figuring BB quite likely just had two pair, and MP2 probably just made trips, and then I would have really hated it when it came back two more to me and I had to decide in the now much bigger pot if I was in fact drawing dead with my flush draw and gutshot.
Anyway, the river fold did save me 2 BB's, like Private Joker mentioned, but it was a little risky, as if I had been wrong, I might have thrown up on my computer.
Thanks for the responses.