The best bit of Celeste and Jesse Forever is the opening credits, a tightly edited series of still images set to Lily Allen’s Littlest Things. It’s sweet, funny and affecting. Unfortunately the actual film is mostly none of these. Rashida Jones is a luminous screen presence and can definitely carry a film but she has written (with Will McCormack) a pretty but superficial, mostly unfunny comedy-drama. In a year where Lena Dunham’s Girls has considerably upped the stakes of story-telling from the perspective of young women in relationship and employment flux this just doesn’t cut it.

Jones’ Celeste is a successful and ambitious woman who lives with her best friend and ex-husband Jesse (Andy Samberg). They’ve handled their break-up in adult fashion and remain very close buddies, although slacker artist Jesse is still carrying a torch for her. She’s keen for him to move on, feeling that he’ll never grow into the man she desperately wants him to be; a situation that becomes complicated when he does and immediately turns his life around in all the ways she hoped for. As her personal and professional world begins to fall apart she starts having second thoughts – only for him to drop a bombshell that threatens to end their friendship and extinguish any possibility of a reunion. All good material for a funny, potentially dramatic relationship comedy, right?

Jones is engaging in the lead and better than the thin material she and McCormack have written. She’s unafraid to paint herself in a bad light throughout in ways that are relatable and human. But there are two serious problems with Celeste and Jesse Forever, which are especially damaging given that the film is essentially a romantic comedy  One, the script simply isn’t ever remotely amusing. I saw it four weeks ago and I can’t remember a single standout line or scene from it. The films’ DNA has evaporated faster than a free Vogue perfume sample. The banter feels too forced and the situations tired. The movie brings to mind complication comedies like the recent Friends with Benefits (in which both Jones and Samburg appear, briefly) which, although pretty forgettable, is like Annie Hall in comparison with this. Most disastrously Jesse, while likeable-ish, is not especially funny or interesting which means that the potential drama in the will-they-won’t-they situation never catches fire.

The supporting characters are the best thing in the film. Not Elijah Wood (who misfires in a badly written, stilted role as Celeste’s GBF) but ace cameo man Chris Messina shines as a potential suitor for Jones and the lovely Emma Roberts is funny and flip as a bratty pop star Jones is promoting. They feel human, funny and unforced in ways that only serve to highlight how mundane the lead relationship is.

In the film’s final third Jones ups the stakes and strives for more dramatic impact as the clock ticks on her and Jesse’s relationship. But by then it’s too late. It may only be 89 minutes long but due to that preceding hour of polite flatness it seems like Celeste and Jesse goes on forever.