Forget Asta, Nick and Nora Charles' yappy, cue-ignoring terrier. "Nick & Nora," Broadway's "big" musical for 1991-92, is the REAL dog.

Styled as a classy stage musical version of Dashiell Hammett's beloved sleuths (immortalized by William Powell and Myrna Loy in the popular "Thin Man" movies of the '30s and '40s), "Nick & Nora" was pitched as "a murder, a marriage, a musical." But, according to Monday morning's critical quarterbacks, it's also "a mess."Troubled almost from the moment of its inception, the $4.3 million musical - which finally had its much-delayed opening on Broadway Sunday, after two months of previews - has already had more lives than a cat. And if you believe the critics, No. 9 has just come and gone.

The New York Times' Frank Rich, who for once won't have to shoulder all the blame for killing a show, called "Nick & Nora" " . . . an instantly forgettable mediocrity."

Clive Barnes of The New York Post wrote, ". . . what we have here is a bad idea turned sour . . ."

Newsday's Linda Winer judged "Nick & Nora" ". . . long, flat and boring."

Michael Kuchwara of the Associated Press called the musical

". . . a half-hearted, sporadically entertaining show, marred by an unsavory, almost schizophrenic book, an unfocused score and one piece of major miscasting."

Trying to get at the mystery of why a musical as potentially promising as "Nick & Nora" flopped is a great deal more intriguing than the confusing, who-cares murder mystery concocted by director Arthur Laurents. It's not that the concept couldn't work; after all, "City of Angels" - another lavish musical about a singing and dancing Hammett-inspired detective who spoofs his way through a period mystery full of gorgeous dames and sinister shenanigans - won both rave reviews and Tony Awards.

But "Nick & Nora's" road to Broadway has been bumpy from the start. The show's original (and inexperienced) producers, James Pentecost and Charles Suisman, came up with the idea of setting Nick and Nora Charles to music in 1985 after watching a double bill of the old "Thin Man" movies, those movie confections buoyed by style and wit and unconscionable numbers of dry martinis.

The producers needed more than two years to get the rights to the material, but by early 1988 they had a musical "dream team" in place - book and direction by Laurents ("Gypsy"), music by Charles Strouse ("Annie"), lyrics by Richard Maltby Jr. ("Miss Saigon").

Several backers' auditions were held, but less than half the money was raised by the time a "Nick & Nora" workshop was staged in August 1990. Barry Bostwick, who plays Nick, came down with malaria, so lyricist Maltby subbed for him. No more money came in.

Last January, Pentecost and Suisman dropped out as producers. Terry Allen Kramer, Charlene and James M. Nederlander, Daryl Roth and Elizabeth Ireland McCann took over, sending Nick & Nora to Broadway - and now, in all likelihood, to oblivion.

The musical had five announced opening dates: first in February, then April, then Nov. 10, then Dec. 2, and finally Dec. 8. The first two delays were to allow for more fund raising. The switch from Nov. 10 to Dec. 2 gave the creative team more time - Laurents tinkered endlessly with the book, and Strouse and Maltby wrote nearly 60 songs for the 15 slots in the show. Meanwhile, a cast member was replaced, and costumes and set pieces were changed - all as "Nick & Nora" spent NINE WEEKS working out its problems before audiences paying a top ticket price of $60.

The final delay came from a widely publicized dispute with New York critics. According to the show's publicist, several complained that if "Nick & Nora" opened Dec. 2, they'd have to work over the Thanksgiving weekend.

But the real dispute with the press involved those pricey preview tickets. No discounts were offered, nor were the performances advertised as previews. "Nick & Nora" just kept running through an ever-longer tryout period as critics were kept from passing judgment.

On Nov. 10, Newsday's Winer wrote: "Can "Nick & Nora" . . . keep charging $60 for previews without somebody telling audiences that they're paying opening-night prices to watch practice?"

Problems among the show's collaborators also were legion, widely reported and much gossiped about. Strouse and Maltby got along well. Strouse and Laurents did not.

"It's been the weirdest collaboration that I have ever been in on in my life," Strouse said over breakfast in early November. "You couldn't pick three more disparate people and say, `You do a show together.'

"Our backgrounds are so different. Our tastes, our temperaments. Richard is the sweetest man in the world. Arthur, on the other hand, is one of the most tyrannical . . . "

Then Strouse, clearly pained, refused to say more.

With creators contentious and quarreling about style, with producers scrapping with critics, is it any wonder "Nick & Nora" didn't work?

After I saw "Nick & Nora," I had dinner with a friend at Joe Allen's, a theater district restaurant whose walls are bedecked with the posters of famous Broadway flops. I wondered then if the "Nick & Nora" poster would be among them.

Now, I wonder where it will go.