Ljubicic won his seventh straight match in the tournament by beating Florian Mayer of Germany, 6-3, 6-3.
Elsewhere, Andy Roddick of the U.S., the No. 3 seed, beat Argentina's Jose Acasuso, 6-0, 7-6 (7-2); Richard Gasquet of France beat qualifier Alejandro Falla of Colombia, 7-6 (7-4), 6-3; fifth-seeded Fernando Gonzalez of Chile topped former world No. 1 Carlos Moya of Spain, 6-3, 6-4; crowd favorite Jurgen Melzer of Austria beat No. 7 seed Juan Carlos Ferrero of Spain, 5-7, 7-6 (7-5), 6-3; eighth-seeded Novak Djokovic of Serbia beat Tomas Zib of the Czech Republic, 6-3, 6-4; and Dominik Hrbaty of Slovakia ousted sixth-seeded Tommy Haas of Germany, 6-3, 4-6, 6-0.