Sainz v. Anderson

So, question.  During my game against formidable Expert Ignacio Sainz, I did pretty respectably, but blundered away a pawn.  Eventually we got to an interesting endgame

[Event Markowski Open]

[Date 1-7-08]

[Site San Diego]

[White "Sainz, Ignacio"]

[Black "Anderson, Caley"]

[Opening "French Winawer"]

1. e4 e6 2. d4 d5 3. Nc3 Bb4 4. e5 c5 5. a3 cxd4 6. axb4 dxc3 7. Qg4 cxb2 8. Bxb2 Ne7?! {8...Qe7!} 9. Qxg7 Ng6 10. Bd3 Rf8 11. Ne2?! Qg5 {I see no reason not to play 11. Nf3 instead, protecting White's only real weakness} 12. O-O h6! {Answers the threat of f4 and therefore makes multiple threats that nearly force White to relieve some of the tension in the position, and thus, some of the advantage he's built up.} 13. Bc1 Qxe5 14. Bxh6 Qxg7 15. Bxg7 Rg8 16. Bd4 Nc6 17. Bc5 b6? {It's funny how in an earlier position, you can analyze all sorts of things based on the fact that the a-pawn of pinned, but then completely forget about it later.  Black does get some compensation, though, the game is far from over.  17...f6 or 17...Nge5 seemed better.}  18. Bxb6 Nxb4 19. Bxa7 Nxd3 20. cxd3 Ne5 21. d4 Nc6 22.Bc5 Ba6!? 23. Rfb1 Kd7 24. Rb6 Rfb8 {White does not win material here because of the back-rank mate weakness that appears should he try.} 25. Nc3 Rxb6 26. Bxb6 Bb7 27. Rxa8 Bxa8 28. Bc5 Nc8!? {This move gets an interesting move for being illegal.  I had originally touched the knight to h7 without taking my hand away, but noticed last-minute that it hung there.  So then from there, naturally, it goes to c8 instead.  My opponent did not notice, nor did I until just now.  It turns out to be essentially irrelevant, or at best harmful to Black.} 29. h4 Ne7 30. Bxe7 Kxe7 31. f4 Bc6 32. Kf2 Kf6 33. g4 Kg6 34. Kg3 Be8 35. Ne2 f5?! 36. g5 Bf7 37. Nf3 Be8 38. Nf5 Kh5 39. Ne5 Ba4 40. g6 Kh6 41. h5 Be8 42. Kh4 Ba4 43. Nf7+ Kg7 44. Kg5 Bd7 45. h6+ Kf8 46. h7 e5 47. h8=Q+ Ke7 48. Qxe6+ Be6 49. g7 Kxf7 50. Qxc6+ Kxg7 51. Qe7 Kh8 52. Kg6 53. Kg8 Qe8#

So, my question- where did I blow this endgame?  I didn't think I was lost after I dropped the pawn.  I thought that perhaps my fatal error was f5, but I can't really find any improvements.  Perhaps I went wrong somewhere after that?

-Caley