CONSPIRACY THEORY

Starring Mel Gibson, Julia Roberts, Patrick Stewart, Cylk Cozart

Director Richard Donner

Opens July 25

That mortals can hold their own against the dynamic duo and a herd of dinosaurs? Producer Joel Silver is betting on Roberts and Gibson, whose salaries (price for the pair: $31 million) account for just a little less than half of this thriller's budget. Gibson, in his fourth collaboration with his Lethal Weapon director, stars as a paranoid New York City taxi driver who pursues Roberts, playing a justice department attorney, and persuades her to take his latest conspiracy claim seriously. Off screen, getting the two overworked superpowers together wasn't so simple: Silver stomped to the reticent Gibson's office with boards and nails in hand, threatening to bar the actor's exit if he said no. ''I thought, That's pretty funny — maybe the movie will be funny,'' says Gibson. To woo Roberts, the producer serenaded her with a brass band — and $11 million. ''Mel could do a great job with Benji the dog,'' says Silver, ''but the girl in this movie was more than just an arm piece.'' As the movie wrapped, the ending was still in doubt: Test audiences decided which of two options, now in the can, would be used. Talk about competing theories. UPSIDE Gibson's recent track record indicates a hit. DOWNSIDE Roberts can't claim the same.