http://de.lichess.org/OW66fMJW#30move 15. It says that 15...Nxe4 is a mistake but it is indeed the best move. Instead the move 15.Ne3 is a mistake. Better is 15. Qb3.
I'm trying to investigate the cause of this issue. My development instance is returning an evaluation of "0.5" for every move every time it analyzes a game, so I must not be testing correctly.
SF evaluation abruptly changes at depth 19 if I spotted it right.
(Damn, this was the hardest captcha, I've had here:
http://i58.tinypic.com/11i1ll5.png)
As far as I know, this is just a quick analysis.
Deep Fritz 14, Komodo and Stockfish all find 15...Nxe4 as the best move after a certain depth.