There seems to be an obvious critical position here:
Black is up a knight for a pawn in this position, and Fritz 9 thinks black is clearly winning after Nc7 (33.Ra5 and here's the move that I missed in my analysis - Bc6! which prevents white from pushing the pawn and creating threats of queening.) Had I seen this I probably wouldn't have made the sacrifice in the first place, but I missed it and I think Sardodos did too because he played Nc6? which allowed Rxb7! and a clear advantage to white.