"Hairspray" is infectious, no doubt about it, both in its upbeat parable about pursuing your dreams and fighting prejudice and in Marc Shaiman's cheery, danceable score.

I suspect I'm particularly susceptible to the score's juicy joy because it's such a clever approximation of the pop music of my youth. But at Tuesday's opening, the audience had a large share of young people, and they certainly bounced up and down and cheered the music as much as I recall others doing in 1962, which is when the story is set.

That story is about chubby (plump?) teenage Tracy Turnblad, who through force of sunny personality overcomes prejudice against her appearance to get to dance on the American Bandstand-like weekly TV show, capture the heart of studly Link Larkin and in the process integrate the show in a time of de facto segregation.

Really, it's just about impossible not to like "Hairspray," it's such a canny channeling of the bright pop sounds associated with early rock, Elvis and Motown. The heros are adorable underdogs and the villainy of the villains is as obvious as the hair-sprayed haystacks on their heads.

There's even a high incidence of adult wit in the lyrics and dialogue, and a refreshing frankness about that dual prejudice about race and size.

All of which makes me glad that this is the second appearance of a tour here -- the national tour came through almost exactly three years ago -- so that it isn't just those of us who have seen the Broadway production, now in its sixth year, who can testify that this one does not measure up.

The problem isn't the dancing and the energy of the ensemble, which are fine, or the sets, which are sketchy in the way that tours often are in their later years. It's the acting, which is generally simplistic and cartoony. Granted, "Hairspray" itself is a cartoon, a lot of fun wrapped around a heartwarming moral. But the characters should have more feeling and depth, anyway.

The greatest disappointments are the older actors, especially Dan Ferretti, who plays Wilbur, Tracy's father, as an animated jumping jack, with none of the sly humor other performers have provided. As a result, "Timeless to Me," the wonderful number where he and his mountainous wife, Edna, do a wryly romantic softshoe, is nothing like the affecting show-stopper it could be.

Under Matt Lenz's direction (however based on that of Jack O'Brien), that overplaying can be seen elsewhere, even in Brooklyn Pulver's Tracy. She's energetic and appealing, a capable singer and an adequate dancer (although Tracy is supposed to be an extraordinary dancer), but she sacrifices potentially truthful acting moments to overstatement. There's more consistency in Sharon Malane's cute work as her ugly duckling pal, Penny.

Greg London, playing Edna in drag, gives an appropriately measured performance -- Edna needs no overemphasis -- but he lacks the personal sizzle of other Ednas. And his fit of self-amused laughter in that duet (the kind of thing the Carol Burnett Show thrived on, what the British call "corpsing") seems planned, self-indulgent schtick.

Only back at my computer, pondering the odd weaknesses in an otherwise lively production, did I look at the program and discover this is a non-Equity tour. In other words, the overwhelming majority of professional musical theater performers weren't available, which helps explain the acting shortfall. It's the more noticeable because PNC Broadway generally hits a higher standard, rarely dipping to non-Equity tours.

You can always find talented young people, though, so the ensemble work is bright and busy.

And however staged, "Hairspray" does have that Mark O'Donnell-Thomas Meehan book and those Scott Wittman-Shaiman lyrics, full of surprisingly witty, un-PC wisecracks about such semi-taboo topics as race, class, sex and weight. In the midst of its colorful regression to hopeful youth, set to the rhythms of throwback pop, there are these little zingers from the real world.

The frank confrontation of racial stereotype is also surprisingly adult. The parallel between the oppressions of segregation and of the prejudice Tracy suffers from being plump is a bit facile, but it is a way to dramatize both.

All this makes it a perfectly appropriate show for bright children. And in spite of my disappointment about the acting, I was certainly born along on the tuneful flood of effervescence.