It’s easy to see why Reese Witherspoon, mired in a slight slump from success that would give convulsive fits to her overachieving characters, would choose a movie such as Just Like Heaven.

The film is a cutesy, classy, semi-charming romance with light paranormal touches. Go-getter doctor Elizabeth (Witherspoon) dies in a car accident. David (Mark Ruffalo), a guy with issues to be disclosed in the second act, sublets her apartment and starts to fall for her lingering, nagging ghost.

But the script also attempts to bulk up by addressing a social issue. There will never be another date movie raising the Terri Schiavo question, at least not one that will open on 3,000-plus screens. And aside from credit for originality, that plot point at least offers an interesting spin on the inevitable mad dash through crosstown traffic that must happen in every whimsical romance.

Just Like Heaven somehow finds an inoffensive, so-so groove even as it’s wildly disjoined. It flirts with morbid issues like life support, numbing grief after sudden death and an existence without experiences. But it also strives to elicit feeling from the romance and laughs from Ruffalo’s perpetual confusion, physical comedy and Jon Heder (Napoleon Dynamite) as a laidback psychic.

The movie succeeds best when Witherspoon and Ruffalo are left alone to ruminate on their characters’ respective in-limbo lives, freed from the gimmick-heavy plotting and very obvious twists. There’s a notable bump as the pair attempts to trace the social missteps of Elizabeth’s life, and these scenes allow Witherspoon the priceless one-liner: “I may have been a lonely home-wrecking whore, but I saved lives.” (She dials down her usual Type A personality nicely here.)

Some of the comedy translates, too, albeit mildly. Ruffalo now has officially exhausted all possibilities as a stumblebum romantic lead (this, 13 Going on 30, View from the Top). Several laugh-out-loud moments counter his sad beer-and-lounge-pants lifestyle, but the movie never is transporting enough to make you forget its fast-and-loose comic play with Elizabeth’s transparency.

Unfortunately, Heder only modulates his Napoleon Dynamite voice into slacker slang (“dude” and “righteous” definitely will not become the new “sweet” and “luck-ee!”). It’s a poor follow-up to his breakthrough performance that, at best, speaks to bad direction and, at worst, speaks to marketing moves from DreamWorks to lure teens in. (Marketing fingers are gooey with pieces of this movie’s pie, given its soundtrack of adult-alternative remakes of oldies and 1980s classics.)

Heder’s misuse is indicative of the film’s lack of any good supporting characters. Oda Mae’s sisters in Ghost had more spark in about half the screen time as Heder, Donal Logue (as David’s supposedly “moral-free” buddy), Ivana Milicevic (a dim-bulb temptress with her eye on David) and Dina Waters (as Elizabeth’s sister). In particular, Logue is used purely as a third-act plot device.

The movie’s sort-of-works pattern plays out as you watch it. Just after effective bits of dialogue about memories of the dead (likely penned by co-writer Peter Tolan, who deals with it weekly and brilliantly on FX’s Rescue Me), Witherspoon and Ruffalo “touch” hands to the eye-rolling sound of otherworldly chimes.

Despite some original strokes and funny gags, Just Like Heaven is a “what-if” romantic comedy that takes too many of its answers from other, better movies.