Britney Spears suffered a hair malfunction during her Circus act this week, when a backing dancer accidentally yanked a handful of hair extension from her head.

In a new YouTube.com video of one of her most recent shows in North America, a suspended member of her troop pulls the singer up into the air with him, leaving behind a big clump of blonde weave.

Meanwhile, insiders claim Britney is struggling with her energetic dance routines.

A source tells Britain's The Mirror, "The choreography is insane - it's so fast it is really taking its toll on her. There is one move during (the song) Touch Of My Hand, where two guys dangle from the ceiling and pick her up upside down, which is really getting to her.

"She spins around for nearly five minutes some nights. The blood rushes to her head and when she gets down she complains of nausea and dizziness. There have been a couple of times when she ran off stage and vomited."

See Brit's hair-raising moment below: