We all know that the stock market has been plummeting in recent weeks. But what's dropping even faster is the stock Hollywood studios put into the value of movie stars. This past weekend's disastrous opening of Warners' costly "Body of Lies" was just another nail in the coffin. Buoyed by the presence of two mega-stars, Leonardo DiCaprio and Russell Crowe, with Ridley Scott in the director's chair, the Middle East spy thriller was supposed to easily win its weekend. Instead, it finished No. 3 -- behind "Beverly Hills Chihuahua," a Disney talking-dog movie, and "Quarantine," an anonymous low-budget thriller from Screen Gems -- grossing a paltry $13.1 million.

The math is ugly. In the past, Warners had spread the risk around. If you look back at other expensive Warners flops, the studio was always shrewd enough to recruit a partner who put up a hefty piece of the budget, as it recently did with "Speed Racer" (co-financed by Village Road Show). But for "Body of Lies," which Warners insists cost less than $100 million (rival studios say higher), Warners had no safety net -- it put up all the money, which means the studio could take a substantial loss.

Warners isn't dumb. It didn't have a partner on the picture because it believed that a Ridley Scott film with two giant movie stars was a pretty good bet. It wasn't. There are always a thousand explanations bouncing around Hollywood when a movie fails (e.g., no one wants to see movies about politics or the Middle East, studios are cannibalizing the market by releasing too many movies, moviegoers are distracted by the bad economy and the dramatic presidential race). But guess what? That didn't stop "Beverly Hills Chihuahua" from opening well -- or the sci-fi thriller "Eagle Eye" just before it.

Crowe and DiCaprio (and Johnny Depp and Tom Hanks and Brad Pitt et al.) get paid huge sums of money because they are supposed to open movies. Period. When you sign a contract with Crowe, it doesn't have an asterisk next to the $20-million salary commitment, saying, "Oh, by the way, this doesn't apply to Middle East thrillers, period boxing dramas, westerns or cute comedies set in the South of France" (just to name a few Crowe movies that -- ahem -- haven't been gigantic box-office successes).

Paying a movie star $20 million is supposed to be a high-percentage bet, a way of giving studio chiefs a reasonable chance at getting a good night's sleep in the weeks before a film's release. But there's a growing tension today between the kind of material movie stars want to do and the kind of material studios want to build their slates around. Having spent years honing their craft and building an image, most stars want a dramatic challenge -- they don't want to stand in front of green screens for three months.

With the adult drama being a genre that's almost dead at most studios, it's increasingly hard to find a common ground where stars can jump into challenging material that studios see as marketable material at the box office.

Studio chiefs know all too well how perilous it can be to try to find material that satisfies movie stars' desire to stretch their acting skills while still serving the studio's need to turn a profit. I'd look like a hypocrite to criticize Warners for making "Body of Lies" after endlessly complaining that studio slates are dominated by so much popcorn schlock. But where is the middle ground? Warner Bros. chief Alan Horn gently chided me Monday for being the first to call when the studio has a failure with a challenging film.

"I know we get criticized for doing mindless popcorn pictures -- and that's fair to a point," Horn told me. "But this was our opportunity to step out and try to do something bold, that's more than the easily digestible fare that all studios, including us, tend to do. 'Body of Lies' had a great script, a classy director and a really interesting take on our country's role in world events."

Horn took issue with my theory that the actors, not the studios, want to make challenging fare. "We all wanted to do this film, starting with (studio production chief) Jeff Robinov and myself," he said. "This wasn't the actors coming to us, begging us to do it. We believed in this movie. We weren't saying, 'Oh, we've protected ourselves by having the comfort of a couple of movie stars, so we'll come out OK.' Russell and Leonardo were cast because they are great actors who happen to be movie stars, not the other way around. They were right for the material."

Horn says each actor took a "substantial reduction in his fee" to do the film. "They did it because they really liked the story." Though he wouldn't divulge what the movie cost to make, he said the biggest chunk of "Body of Lies' " budget was spent on below-the-line production costs, largely because of Scott's desire to shoot in Morocco and deliver a film with a bigger-than-life size and scale. Horn also cautioned that "Body of Lies" could perform better overseas, noting that the 2006 DiCaprio thriller "Blood Diamond" made roughly twice as much money overseas than it did in its U.S. theatrical run.

Fair enough. We'll acknowledge that the final box-office jury hasn't rendered a verdict. But I've talked to a growing number of industry experts who worry that movie star stocks are still overpriced, making a persuasive case that younger audiences are far less loyal and far more immune to movie star charms than past generations. Media savvy, marketing resistant, these kids simply have less emotional investment in movie stars than ever before. Star power will be put to the test a number of times in the coming months: Will audiences go see DiCaprio in the period drama "Revolutionary Road" later this fall? Can Brad Pitt wow moviegoers, as well as critics, going backward in time in "The Curious Case of Benjamin Button"?

For now, most studio slates are increasingly being built around movies that are movie star-free zones. With the exception of hiring Johnny Depp to take the helm of its "Pirates of the Caribbean" franchise, Disney rarely uses top stars, preferring to build its business around animated pictures and modestly budgeted family fare that is sold on concept, not star power.

The Disney formula hasn't gone unnoticed. I was on the phone last week with a rival studio chief who said that, once you got past Will Smith, it was hard to list one major movie star who could open both popcorn fluff and more serious dramatic pictures. Every studio head has to be rethinking the movie star issue right now, having seen film after film fail to succeed at the box office despite the presence of major stars.

Universal Pictures, for example, has been poised to greenlight "Nottingham," an expensive period Robin Hood film that would re-team Crowe with Scott. . It wouldn't come as a surprise to see "Nottingham" go back to the drawing board, with Scott being forced to re-imagine its scope to keep its budget at a more manageable level.

No one's saying Hollywood is going to suddenly end its love affair with movie stars. In a business built far more on perception than reality, they are the straw that stirs the drink. But after openings like "Body of Lies" had this weekend, it's time for a market correction.