THE TRAILER FOR A Dirty Shame looked so great that one hoped John Waters had actually found his way back to the peak form last glimpsed in Hairspray, Polyester, and Female Trouble (depending on your degree of purism). But the trailer lied. Shame is just as much of a mess as Cecil B. Demented was, and with fewer incidental laughs. The concept, which shoots its wad pretty much in the first reel: people who get hit on the head (any old way; it doesn't seem to matter) become raving sex maniacs. That's good news for thoroughly repressed Baltimore housewife Sylvia Stickles (Tracey Ullman), her criminally underlaid husband (Chris Isaak), and the gigantically siliconed ex-stripper daughter (Selma Blair) they've locked in the attic for chastity's sake. It's bad news for all the "neuters," those upstanding citizens who prefer to keep their sex vanilla, infrequent, and absent from public display. In zombie-flick style, they're soon running for their lives from an epidemic of pleasure-seekers led by "sex saint" Ray-Ray (Johnny Knoxville). There's so much potential in this simple setup that you'll wish there was a John Waters around to do it justice ... oh, wait. What can be said? This movie's jokes are like water balloons lobbed at a barn door two feet away. It's of the school wherein just saying naughty words, or sticking tongues out at the camera, isn't just expected to be funny – it's expected to be funny over, and over, and over, and over. The film in-jokes aren't much even if you get them, and the usually colorful cast is stuck spinning wheels in overdrive throughout. Here's what's really a dirty shame: that in 2004, John Waters can't make juvenile sexual humor any more imaginative (or less dull) than one might expect from, say, Porky's XII. Depressing. (Dennis Harvey)