Has Star Trek's movie franchise reached the final frontier? Paramount execs are still puzzling over the dismal $43 million domestic gross of last December's Nemesis (left), the worst ever for a Trek film. ''It was a very big disappointment to us and remains a mystery,'' Paramount chair Sherry Lansing tells EW. Since exit polls suggest the $60 million sequel was a fave among Trekkers, Lansing adds, ''We can only assume that the fan base in some way has shrunk.'' Such comments have some devotees reaching for their phasers. Mark Anbinder, VP of Starfleet, the International Star Trek Fan Association, laughs that Paramount ''failed to get anyone but the fan base in the seats'' for Nemesis -- and barely reached that base. ''I haven't even seen it a second time.''