LAS VEGAS -- The rule of thumb in the concert industry is that Canadians generally have to endure a frustrating wait of four to six weeks between the time a major tour hits the road and the time it finally makes its way to the Great White North.

 And, after witnessing the spectacularly sloppy dress rehearsal that passed for the opening concert of U2's PopMart tour here Friday night, we should all be grateful.

 After trying to cram what should have been months of production time into a few scant weeks, the overambitiousness that U2 has, to this point, thrived upon, finally caught up to them, and it did so in front of a sold-out crowd of 38,000 very forgiving fans at Sam Boyd Stadium.

 From missed cues, to out-of-tune instruments, to a horrendous sound system, to flat-out musical breakdowns -- the band actually stopped in the middle of both "Staring At The Sun" and "Discotheque" because they simply couldn't get it together -- this was an obvious case of U2 simply not being ready to play for a paying audience.

 The good news is that last night's sprawling, 130-minute mess still displayed enough moments of raw inspiration that, given the talent (not to mention the resources) of all involved, however, it's not hard to imagine it rounding nicely into shape by the time the PopMart tour makes its Canadian debut, June 12 in Winnipeg.

 Opening with a pounding, taped version of the 1979 hit, "Pop Muzik" by M (a.k.a. Brit studio wiz Robin Scott), the evening got off to a raucous start as Bono, The Edge, bassist Adam Clayton, and drummer Larry Mullen Jr. surprised everyone by emerging from the middle of the crowd and climbing onto the runway that extends out into the audience.

 Decked out in suitably garish outfits -- Clayton, decked out in an orange radiation suit, resembled a member of new wave kings Devo -- they slammed into a confident version of "Mofo," one of the highlights of the endlessly analyzed "Pop" album.

 With Bono shouting "mother, mother" at the end of that song, the band then reached all the way back to its first album for "I Will Follow," the roaring anthem inspired by the death of Bono's own mother.

 But after a muscular run-through of "Even Better Than The Real Thing" -- which showcased the band's vastly improved rhythm section -- things quickly spiralled out of control. Bono's voice cracked during a sluggish "Do You Feel Loved," and the rest of the group seemed to sprout roots on the soles of their shoes, a problem exacerbated by the fact that the towering LED screen behind them continually flashed 50-foot-high images of them standing stock still.

 The moments in which U2 managed to transcend the unresolved grab bag of concepts supposedly manifested in the giant yellow arch, the monstrous olive-on-a-swizzle-stick, and the 40-foot mirrored lemon that make up the stage set were few and far between, but they were there.

 A rumbling "Miami" segued into a surprisingly funked-up reworking of "Bullet The Blue Sky;" The Edge led the crowd in a goofy singalong to, of all things, The Monkees' "Daydream Believer," which he introduced as "my favorite Bob Dylan song." And "Where The Streets Have No Name" can still pull a crowd to its feet in a split second.

 Even the humiliating version of "Discotheque" -- which seemed to disintegrate right beore our ears -- was at least preceded by a spectacular special effect: the band emerging from the giant mirrored lemon like aliens landing on a foreign planet.

 A contrite Bono summed the evening up succinctly after a crowd-pleasing performance of "Mysterious Ways," "Okay, so we f----- up."

 Yeah, but one thing you can say about U2: they always seem to find a way of using their mistakes to create something new.

 With any luck, they'll discover what that is and apply it to PopMart -- and do it some time in the next six weeks.