One would think that a sophisticated romantic comedy about finding love in middle age, written and directed by a successful filmmaker and starring two of today’s most respected and beloved actors, would be a hands-down sure-fire winner of a movie.

There’s a chance one might be wrong.

“Something’s Gotta Give” has terrific potential. It’s penned by Nancy Meyers, who began her career by writing “Private Benjamin” and has written, produced and directed several light and sweet comedies like “Father of the Bride” (1991) and “The Parent Trap” (1997). Her success as the director of the highly watchable “What Women Want” would be enough reason to expect a lot of her latest film.

And who wouldn’t love Jack Nicholson and Diane Keaton as two very opposite middle-aged singles who start out as enemies and end up as soulmates? Both are brilliant in their roles as an infamous womanizer and a divorced playwright, respectively.

And as if those two names weren’t a big enough draw, their supporting cast is no small potatoes either. Amanda Peet plays Keaton’s daughter, who’s dating Nicholson at the start of the story. Frances McDormand, always likable, appears as Keaton’s sister; and Keanu Reeves is wonderfully charismatic as Nicholson’s doctor, who’s smitten with Keaton’s character.

The first hour of this two-hour 13-minute movie is delightful and witty. Peet is bringing Nicholson to her mother’s beach house in the Hamptons (which she assumes is empty) for their first intimate weekend. After some initial awkwardness when Mom shows up unexpectedly, all decide to stay, even though Keaton and Nicholson bristle at each other like static-charged sweaters.

Suddenly, Nicholson has a heart attack, and doctor’s orders are not to leave the area. So he’s obliged to stay and rest up in Keaton’s home, an arrangement that neither are thrilled with. But gradually, they learn to appreciate, then respect each other, and before they even realize it, boom – they’re in love, although neither can quite admit it.

Once he’s pronounced well enough to travel, though, he heads back to New York and the movie takes a swan dive. From here on, audiences follow both leads as they dance around their own feelings and try to deal with the heartbreak they’re both undergoing, but in vastly different ways. Keaton does have a fabulous scene where she bawls hysterically and fuels her writing with her raw emotion.

Writer/director Meyers wrote the screenplay with these two actors in mind, and said she wanted not only to explore male-female role issues, but also age issues and life philosophy issues. But that’s where “Something’s Gotta Give” gets too thin. There are too many issues floating around for viewers to focus on one in particular.

Plus – I’m sorry, but it’s difficult to feel too sad for the upper middle class. Even when their hearts are trampled on, they can still go wallow in their pain at their beach house in the Hamptons, for goodness sake.

So we spend another hour watching these two wrestle with their heartache before the cheap, tidy ending comes along and wraps up the film. One might wonder if cutting off the story at the point where they first part company would have been a better choice. Viewers would have to guess what else, if anything, happened between them instead of sitting through the bogged-down second half that contains very little romance and zero comedy.

So what gives in “Something’s Gotta Give?” Regrettably, the audience’s attention.

‘SOMETHING’S GOTTA GIVE’

Rated PG-13 for sexual content, brief nudity and strong language

Starring: Jack Nicholson, Diane Keaton, Amanda Peet, Keanu Reeves

Director: Nancy Meyers

Length: Two hours 13 minutes

Now playing at: Astoria Gateway Cinemas, Cannes Cinema in Seaside

Short take: Jack Nicholson and Diane Keaton are wonderful as two middle-aged singles who unexpectedly fall in love. The first half of the movie is light and comical, but the slow, unfunny second hour is a big disappointment.

Rating: Two and a half stars

Movie trivia: What distinction does Jack Nicholson hold in regard to the Academy Awards?

Answer: Nicholson holds the record for most Oscar nominations, with 12. He has won three.