It's time to scrape that ''Houston, we have a problem'' bumper sticker off the back of the car. Summer-movie season is upon us, and a new crop of catchphrases are about to bombard the lexicon. Besides Arnold ''I'll Be Back'' Schwarzenegger's ''You've been erased'' from Eraser, there's Jim ''Smokin''' Carrey's Cable Guymantra, ''I'll juice you up,'' and Will Smith's Independence Dayreaction to an alien dogfight ''Now, that's what I call a close encounter.'' Since the right phrase can help transform a hit into a cultural phenomenon (i.e., Forrest Gump's ''Life is like a box of chocolates''), the stakes are high. ''You can't manufacture a catchphrase, but if it makes it into the streets, it definitely doesn't hurt the movie's grosses,'' says Susan Pile, MGM's exec VP of worldwide publicity, who is pinning her hopes on the bilingual release Fled, starring Laurence Fishburne. If MGM has its way, ''We gotta fled'' will become this year's ''Hasta la vista, baby.'' But the studio may have an even better parting shot with the Spanish version of the phrase, since, when translated, ''We gotta fled'' becomes ''Yo fled.'' It's no ''Yo, Hunchback,'' but it just might do.