One of these weeks will bring a good new Hollywood comedy in the PG or PG-13 range, midway between the G-rated felicities of "Ratatouille" (though the rating shouldn't deter anyone) and the R-rated effrontery of "Knocked Up."

"License to Wed" is not that comedy.

It's about a young Chicago couple enrolling in a three-week marriage preparation course that feels like three years, in real time.

Sadie (Mandy Moore) comes from money and is the most pleasant, even-tempered woman on the planet. Her beau, Ben (John Krasinski), lacks a personality of any discernible sort. Their puppet master is Rev. Frank (Robin Williams), a tough-love man of God whose course work hits his victims where they live. One rule: no sex until after the marriage. (At one point Frank and his pre teen sidekick, Choir Boy, listen to the couple in the throes of foreplay, and I'm still not laughing.) Another requirement: The couple must wrangle a set of mechanical peeing, puking, wailing robot babies while at the mall.

Williams' grimace is starting to look desperate. Then again, no one comes off well in director Ken Kwapis' handling of this greasy screenplay. The film is perpetually on the brink of turning into something ruder and potentially more interesting ("Bad Reverend"?). Even on its own terms it doesn't hang together; you aren't given enough to believe in regarding the central couple, and the socioeconomic tensions informing the relationship (he's middle-class, she's upper-upper-uber-upper-middle) are raised, halfheartedly, and then dropped.

You'd never know from "License to Wed" that Krasinski is a big asset to "The Office." Here, playing an unappealing male lead, he merely smugs his way through the assignment. Moore, I like; she's a young actress of modest but confident range. Material matters, though. It's a rare performer who could survive many comedies on the level of "Because I Said So" and "License to Wed."