Any company can have an off night. A fumbled line or two, a dropped lyric, a singer out of sync with the orchestra -- these were the minor miscues that befell the touring company of "My Fair Lady" that pulled into Wolf Trap on Tuesday evening.

But even without those glitches, this "My Fair Lady" shapes up as fair, at best. A really good "Lady" lifts you with its warmth; the show can be elegant, lovely and wonderful fun. Drew Scott Harris's production isn't bad, but it never quite manages to plaster a helplessly silly smile on your face.

And it's the little things wot done it in, to borrow a typically Cockney phrase from Eliza Doolittle. Take Marla Schaffel: She's nearly wonderful as Eliza, the grubby flower girl who gets taken up by haughty phonetics professor Henry Higgins. (On a bet, Higgins tries to polish her up to make her pass for high society.) Schaffel speaks with a strong, chesty voice -- her caterwauling vowels are spectacularly crude and colorful -- and it's easy to feel good about Schaffel's singing when she croons "Wouldn't It Be Loverly" with sweet longing. She's also a hoot drinking tea at the Ascot races, salvaging a scene strangely dominated by a mash of clashing colors and patterns in a witless rendering of upper-crust clothing and decor.

Her singing doesn't fully blossom, though, as her songs climax, and a chance for a thrill is gone. Nor does Schaffel's Eliza seem particularly aroused during "I Could Have Danced All Night," and the flatness is partly in the performance and partly in the unhappily lifeless staging (neither Harris nor choreographer Lisa Guignard rises to the occasion; there's no real giddiness, no luxuriating in the moment). The music is dreamy, the character is suddenly intoxicated with love, but the audience isn't taken all the way.

John Vickery is squarely in Rex Harrison territory as Higgins. He has an imperious mien and a kingly roar, and he finesses his patter songs ("Why Can't the English," "I'm an Ordinary Man") in traditional Higgins style like a tone-deaf warbler. But the chemistry is off: Higgins needs to have a touch of the debonair in reserve, or flickers of charm -- something to spark the interest of a lively and discerning girl like Eliza. Vickery, like Schaffel, brings some fresh comic business to a familiar role, yet the Higgins bluster is never quite leavened with romantic magnetism. The script may say these two ultimately hit it off, but this performance says they don't.

Of course, charm is tough to project in a venue as cavernous as Wolf Trap. Maybe that's why Rob Donohoe, as Eliza's rapscallion father, seems every inch a scamp but lacks the twinkle that would bring "Get Me to the Church on Time" to a feel-good finish. (Again, the choreography misses a fizzy chance.) In fact, the show gets off to a slow start thanks to gymnasium acoustics that muddy the fine comedy of mangled language and precise ripostes. What often comes across is the general idea. And as with much of the rest of this show, that has to be good enough.

My Fair Lady, book and lyrics by Alan Jay Lerner, music by Fredrick Loewe. Directed by Drew Scott Harris. Through Sunday at Wolf Trap, Trap Road, Vienna. Call 1-877-WOLFTRAP or visit www.wolftrap.org.

John Vickery plays Henry Higgins and Marla Schaffel is his pupil Eliza Doolittle in "My Fair Lady" at Wolf Trap.