The fourth-seeded Ljubicic, who dropped his serve once in the opening set, had five aces and broke the American's serve three times.
The huge-serving Isner needs only one more ace Friday to reach 1,000 for the season. The 25-year-old American has already served 346 aces more than his previous best last season when he reached 653.
Against Nieminen, Gasquet lost serve straight away and trailed 2-0 but then broke the Finn twice to take the first set.
Gasquet seemed in control when he led 6-4 in the second-set tiebreak but Nieminen saved two match points in winning the next four points to level the match. Gasquet lost when he was broken for the third time in the match.
Nalbandian served twice for the match at 5-4 and 6-5 in the second set. Simon broke him to love on the second occasion to force a tiebreak and then leveled the match. He broke Nalbandian twice more in the deciding set.
Although Montanes won in straight sets, the match was closely contested with Llodra hitting 10 aces and forcing Montanes to save four break points in the opener.