Watching a latter-day Woody Allen movie is like taking an experimental swig of old milk.

Some of the time, you get a pleasant surprise (“Small Time Crooks”), but most of the time, you don’t. Mostly, you’re bummed out by Allen’s sour humor, his bitter treatment of the one-dimensional characters and the curdled, unpleasant aftertaste the whole thing leaves.

Allen’s latest, “Hollywood Ending,” isn’t as coagulated as “Jade Scorpion” or “Celebrity,” but it’s not much fun. He plays a has-been director who gets another shot when his studio executive ex-wife (Tea Leoni) pushes him for a job. He endangers it by casting his idiotic girlfriend (Debra Messing) and by going blind, but, as the title hints, things work out in a way that makes Allen happy with one of the half-his-age actresses who crave his liver-spotted lovin’ (for good measure, Tiffani Theissen also throws herself at him).

The more you know about Allen, the meaner “Ending” seems. If, for instance, you’re aware that his most recent director of photography was a Chinese man who spoke little English, you’ll be astonished by the rude in-jokes about a similar situation. Allen seems to think he’s laughing at himself (someone mentions that his character always goes for foreign cameramen, which is true of Allen, too), but surely he notices that all the cruelty is directed at the Chinese man?

“Hollywood Ending” is Allen’s attempt to do an “Adam’s Rib”-style, bickery comedy, and he does whip out some good lines (“I would kill for this job but the people I want to kill are the people offering me the job”). But Allen lingers over tired Hollywood jokes, dragging down the first half of the film and making the second half seem slower than it is. And his underdeveloped characters have so little to do that even resourceful comedians like Leoni and Messing don’t come off well. Which must be a bitter pill for them to swallow with their icky-tasting milk.