In the on-again, off-again world of show business, it's on-again for Gregory Hines, star of the new Duke Ellington musical "Sophisticated Ladies." Hines was fired by the show's producers Wednesday morning because of differences with director Donald McKayle, but was then rehired a few hours later, after the cast reportedly refused to perform a matinee without him and made an emotional plea on Hines' behalf.

The five producers not only brought Hines back, but proceeded to dismiss McKayle, according to a source close to the show. Those same producers had initially sided with McKayle over what they called "irreconcilable differences." Hines said he was fired for being "very aggressive, maybe too aggressive" in going over McKayle's head about artistic matters.

"I never thought the producers were entirely wrong," Hines said last night, "but I didn't think I deserved to be fired either. I came in and they fired me, so I was on my way to New York. I'd checked out of my hotel." Hines said he heard he was being reinstated when he telephoned a friend in the cast.

By Wednesday night, Hines was back onstage at the Kennedy Center -- in spite of earlier announcements of his departure and replacement by dancer Gregg Burge. Coincidentally, dancer Judith Jamison, Hines' costar, had gone to see her personal physician in New York Wednesday because of possible complications from a needle puncture in her foot.

An understudy filled in for Jamison Wednesday night, but she was back in the show yesterday, after being informed that removal of the needle would call for surgery and weeks of recuperation, while there would be no danger if she postponed the operation.

Hines would not describe his exact differences with McKayle. He said he was "never laying ultimatums on anybody" and could have continued working with McKayle. "I'm not satisfied with any aspect of the show," Hines said, "not the music, the dancing nor the script. This music has stood up for 50 years and the audiences love the show, but as a cast we know there's so much more we can do with it."

"Sophisticated Ladies" was overhauled substantially between its December run in Philadelphia and Tuesday's opening in Washington to mixed reviews (but high praise for Hines). Hines predicted that in a few weeks the show would be improved and the changes would speak for themselves. No new director has been announced.

"This company is one of the warmest, tightest companies I've ever been involved with," he said. "The company rallying behind me was just the most warm demonstration of love."

Mercer Ellington, the show's musical director and son of Duke Ellington, explained: "We get along like family and so we argue like family. Your nerves get to a point where something's got to give. That's what happened."

"We're on the same team now, we're working together . . . and we're gonna stay together. It's gonna be a great show," producer Roger Berlind said early yesterday. Neither Berlind nor McKayle could be reached for comment on the director's departure.

Hines had been upset over the producers' initial statement that he had "left" the show. He preferred to have it known that he had been fired. "I've been fired before," he said. "I was fired once selling guitars when I was a hippy in the early '70s."