Ivanchuk continued 34.Qe3? (34 Qg1 is essential) inviting Black to cut off communications between the white queen and knight with 34...d4. White's intention was to continue 34...d4 35.Qd2 when 35...Qxb6 is met by 36.Rxg6 followed by 37.Qxf4. However, after 35...Rh4! Black threatens both Qxg3 and Qxb6. White may try 36.Rg1 or 36.Be4, relying on a counter-attack against g6, but neither is remotely convincing. According to Ivanchuk, White is lost.
Topalov, however, talked himself out of playing it, instead opting for 34...Rdf8. The game continued 35.Rg1 d4 36.Qd2 when 36...Qxb6 leads to a remarkable draw after 37.Be4! Rxe4! 38.Rxg6! Ref4!! 39.Rxb6 Bd5+ 40.Qg2. Black regains the queen to reach a drawn double-rook end-game.
Instead of that, Topalov blundered (or gambled outrageously) with 36...Ne5? when there followed 37.Be4+ (White can also win with 37.Qxf4! Rxf4 38.Be4+ when 38...Rxe4 allows mate in three with 39.Rg7+ Kh8 40.Rg8+ Kh7 41.R1g7 mate, and 38...Ng6 loses to 39.Rxg6) 37...Rxe4 38.dxe4 Nf3 (38...Qxb6 loses to 39.Rg7+ Kh8 40.Qg2, threatening both Rxg8+ and Rh7+ followed by Qg7 mate) 39.Rxf3 Rxf3 40.Qg2 resigns. 40...Qf8 is met by 41.Nd7 Qf7 42.Ne5.
Here are the moves of Robert Hubner's last-round disaster. He must have totally overlooked White's final move, but at least his position was already bad enough for it to make little difference.
White: Ivan Sokolov
Black: Robert Hubner
1 d4 d5 2 c4 dxc4 3 e3 e5 4 Bxc4 exd4 5 exd4 Nf6 6 Nf3 Be7 7 0-0 0-0 8 h3 Nbd7 9 Nc3 Nb6 10 Bb3 c6 11 Ne5 Nbd5 12 Re1 Be6 13 Bg5 Re8 14 Rc1 Nd7 15 Bxe7 Rxe7 16 Ne4 f6 17 Nd3 Nf8 18 Qf3 Qc7 19 Ng3 Rd8 20 Nc5 Bf7 21 Rxe7 Qxe7 22 Nf5 Qc7 23 Qg3 Qxg3 24 fxg3 b6 25 Nb7 Rd7 26 Nfd6 Be6 27 Rxc6 Ne7 28 Rc3 h5 29 Ba4 1-0.