I had a very similar hand the other day. The street I misplayed is the turn, where I definitely should have raised. I had such a strong read that MP1 was full of crap that I had to blow away the field and make it heads-up to ensure my victory. Luckily my mistake didn't prove fatal, and although I still failed to improve, I called for one bet in a large pot.
Party Poker 2/4 Hold'em (10 handed)
converter
Preflop: Hero is MP2 with 6[img]/images/graemlins/spade.gif[/img], 6[img]/images/graemlins/diamond.gif[/img].
<font color="#666666">
2 folds</font>, UTG+2 calls, MP1 calls, Hero calls, <font color="#666666">
1 fold</font>, CO calls, <font color="#CC3333">Button raises</font>, SB calls, BB calls, UTG+2 calls, <font color="#CC3333">MP1 3-bets</font>, Hero calls, CO folds, Button calls, SB folds, BB calls, UTG+2 calls.
Flop: (18 SB) Q[img]/images/graemlins/heart.gif[/img], 4[img]/images/graemlins/spade.gif[/img], Q[img]/images/graemlins/spade.gif[/img] <font color="#0000FF">(5 players)</font>
BB checks, UTG+2 checks, <font color="#CC3333">MP1 bets</font>, <font color="#CC3333">Hero raises</font>, Button folds, BB calls, UTG+2 calls, MP1 calls.
Turn: (13 BB) 5[img]/images/graemlins/diamond.gif[/img] <font color="#0000FF">(4 players)</font>
BB checks, UTG+2 checks, <font color="#CC3333">MP1 bets</font>, Hero calls, BB calls, UTG+2 calls.
River: (17 BB) J[img]/images/graemlins/club.gif[/img] <font color="#0000FF">(4 players)</font>
BB checks, UTG+2 checks, <font color="#CC3333">MP1 bets</font>, Hero calls, BB folds, UTG+2 folds.
Final Pot: 19 BB
Results in white below: <font color="#FFFFFF">
MP1 has 5s 4h (two pair, queens and fives).
Hero has 6s 6d (two pair, queens and sixes).
Outcome: Hero wins 19 BB. </font>