"Dying is easy. Comedy is hard," English tragedian Edmund Keane supposedly said on his deathbed. Screwball comedy is harder still, however effortless such classics as BRINGING UP BABY and THE PALM BEACH STORY may make it look. Take two temperamental movie stars, Gwen Harrison (Catherine Zeta-Jones) and Eddie Thomas (John Cusack), who made a string of hits together before their golden romance degenerated into tabloid scandal and poisoned their careers. Add one egomaniacal director (Christopher Walken) who's holding hostage the only print of his new sci-fi opus, "Time Over Time," refusing to show it to studio executives before it's seen by journalists (a Hollywood no-no of the highest order), and a rapacious studio head (Stanley Tucci) who's convinced that the only way to make the movie — whatever the hell it is — a hit is to convince fans Gwen and Eddie have reconciled. Stir in complications in the form of Gwen's new boyfriend, volatile and heavily accented Spanish hunk Hector (Hank Azaria), and her formerly fat sister/personal assistant Kiki (Julia Roberts), who's always nursed a secret crush on Eddie. And finally, toss in veteran publicist Lee Phillips (Billy Crystal) who, having just been fired in favor of a callow protégé (Seth Green) who's never heard of BREAKFAST AT TIFFANY'S, is lured back to organize the lavish "Time Over Time" press extravaganza. His mission is to orchestrate the impossible: Keep the stars smiling, distract the journalists so they don't care that they haven't seen the film, and make sure everyone leaves in a feel-good stupor. This sounds like the recipe for a tart, behind-the-scenes look at industry finagling, in which knowing digs at Hollywood's hype machine offset the sweetness of the inevitable romantic finale. But while the film delivers some sharp dialogue, overall it's soft and slightly unfocused, and the audience-gratifying romance interludes get in the way of its potentially lacerating exposé of press junkets, where studio flacks try to wine and dine good write-ups out of the often all-too-obliging media hacks. Roberts exudes her trademark girl-next-door charm (she even appears in a blobby fat suit, spunky star that she is), and Zeta-Jones is pitch perfect as the vain, capricious, creamily beautiful Gwen, but Azaria horribly overplays his Castillian accent and macho posturing. Co-scripter Crystal gives himself most of the best lines and delivers them with barbed aplomb, but the whole thing shambles when it should crackle.