Closed game

In this 15 | 10 game I got what seemed to be a fair position.  I made it a closed game to weaken my opponent's fianchettoed light squared bishop.  I had less space, but I had a bishop that was theoretically good compared to my opponent's bad bishop.  The game was almost entirely closed (in fact if I wanted, I could have made it closed entirely, a likely draw).  However when it opened up, I missed a crucial tactic and lost.

Comments welcome

If black played 33...bxc4, wouldn't white respond with something like Nf1, intending Ne3 on his next move to make black's pawn dead in the water? 

It seems white would be able to end that black pawn's hopes first before making his push with Ra7, but I'm probably missing something. 

The knight can't get to c1 or c2 in time to stop the pawn.  The only way to stop it is with white's queen.

Don't follow you--

33. Qa5 bxc4

34. Nf1 c3

35. Ne3, and now black's pawn can't proceed to c2. 

Yeah I think you're right.  Strange, Crafty takes a long time to see that.  Here is Crafty's line:

So I guess my error must have been earlier than that, maybe with a6 instead of b6.