KSL will break from CBS's planned prime time line-up this fall when the network introduces a new series based on the hit movie "Dirty Dancing," a station official disclosed Friday.

KSL-TV General Manager William R. Murdoch said his station, as well as others in the CBS network, had expressed concern about the program, which is scheduled to play Saturdays at 7 p.m. beginning in November. The concerns, he said, centered one key question: How dirty would the dancing be in "Dirty Dancing"?Murdoch and other KSL officials screened an early "Dirty Dancing" pilot at the CBS affiliates meeting last spring, and they weren't pleased with what they saw - the same kind of physical, suggestive dancing popularized in the movie. Since then the pilot has been changed considerably, and Murdoch asked for a look at the new show. But when producers said they couldn't get a copy to him until about a week before the scheduled premiere date, Murdoch pulled the plug.

"We wanted to be sure the show would be consistent with the values-oriented programming approach we take at KSL," Murdoch said in explaining his decision. "When they couldn't give us that assurance, we decided to make a change."

The KSL executive said his station will play the second half-hour of the hour-long weekend version of USA Today in the time period.

***TACKY AD OF THE WEEK: I can understand KUTV wanting to get a new image for "PM Magazine," what with a new host, a new producer and a new way of doing business coming up the first week of October. But the soft-focus, Yuppie-fied image they're communicating in the new spots for Tami Sanders and John O'Connor seems a bit extreme. I mean, what do these guys think they're making, soft drink commercials?

***SO HOW MUCH TV does America watch? According to the A.C. Nielsen Co., families where the household income is more than $40,000 watch the least - 48 hours and 29 minutes per week, or almost seven hours a day. And remember, that's the group that watches the least. Some lower income groups average well over eight hours a day in front of the ol' electric hearth.

No wonder so many of us are walking around with bloodshot eyes.

***REMEMBER HOW ARSENIO HALL bailed Fox out by stepping in for Joan Rivers after she was unceremoniously dropped from "The Late Show"? Remember how they kept Hall dangling out there while they rushed to prepare "The Wilton North Report" for the time period? Remember how "Wilton North" bombed, and how Fox tried to get Hall to come back but he was already committed to work with Eddie Murphy in "Coming to America"?

Well, guess who's coming back to the time period in January in a new syndicated late-night talk show that will be on opposite "The Late Show" in many markets? That's right - Hall. All together now: "What goes around, comes around."

***VIDBITS: Watch for thirtysomething to introduce a new character to its ensemble when the show returns. According to executive producer Marshall Herskovitz, the new character will be homosexual . . .

NBC has canceled Main Street, the noble-hearted news magazine for youth it has aired on an occasional basis for two years.

NBC News president Michael Gartner cited a lack of advertiser support for the series as the chief cause for its demise . . .