HIGH DRAMA: Sylvester Stallone found himself in some tight spots while filming Cliffhanger, the Alpine adventure due out in May with Northern Exposure's Janine Turner. But the real action is taking place behind the scenes: Lawsuits are flying between Carolco, Cliffhanger's production company, and Mike France, the movie's 30-year-old screenwriter. Carolco has already paid $750,000 to settle disputes with writers who claimed France plagiarized their work; the company is now suing France for fraud and breach of contract. France has filed his own suit against Carolco, asking that his contract be upheld. The irony, says director Renny Harlin (Die Hard 2), is that Stallone rewrote France's script. ''You can see the original script somehow,'' says Harlin, ''but we did change it. It was the typical action-adventure (with dialogue like) 'Let's go. Look out. C'mon.'''