John C. Reilly as Dewey Cox in "Walk Hard: The Dewey Cox Story."

There is nothing that makes me happier than to see John C. Reilly, he of outstanding quirky, nuanced performances in great films such as "Boogie Nights" and "Magnolia."

But it's hardly an auspicious start headlining a film like "Walk Hard: The Dewey Cox Story," a comedy that has flashes of comedic genius, but ultimately falls flat on its face.

"Hard" is the story of Dewey Cox, whose life is eerily similar to that depicted of one Johnny Cash in the recent movie "Walk the Line." For instance, he has to ponder his entire life before going onstage, a childhood accident killed his older brother, he left home at an early age, and developed a drug habit as his star rose.

The parody is obvious on so many levels, but second-generation director Jake Kasdan ("Orange County") -- Lawrence is his dad -- insists on reminding us that they're lampooning musical biopics at every instance, all but turning to the camera and announcing, "Isn't it silly and clichéd that he got hooked on drugs?"

It's almost worse that it bounces from such a train wreck to what is at times brilliant. Examples: The movie skewers genre conventions such as the audience spontaneously rising and dirty dancing (in a lewder fashion than usual), or telling his wife (and kids) how much he loves them, only to hop in the sack with the first bimbo to shake her thang in his general direction (or the first 15 to do so).

When it's bad, it's bad, but when it's good it's worse.

There's nudity of both genders aplenty, though the male side is done to bigger laughs, though none of the principals bares it all (sorry, Jenna Fischer fans).

But it's those times in between the greatness that stand out.

The script was co-written by Kasdan and current comedy god Judd Apatow, but the direction lacks Apatow's graceful knack for dancing on the line between touching and obscene, instead stumbling and stomping the line into oblivion.

When in doubt, it falls back on the tried and true, but in this case should be called the tried and tried again. And again. And again.

Its worst moments are reminiscent of a Wayans brothers film, which is the worst thing I can think of to say about a comedy.

Reilly is fine in the lead, though the material has him doing what amounts to a Will Ferrell impression. He's not quite as capable as Ferrell to make the material seem funnier than it is, but he does as well as can be expected.

He has some legitimate laugh-out-loud moments, but there are just too many jokes that miss, and miss badly.