Beyonce was caught in a real-life EMERGENCY on stage at her concert last night when her hair got tangled up in a stage fan -- and the crew scrambled to free the singer, MID-SONG!!!!! Queen B was performing "Halo" in Montreal when disaster struck ... but like the PRO that she is, Beyonce continued to sing during the incident, NEVER ONCE MISSING A SINGLE BEAT. Eventually, a crew member with a pair of scissors cut Beyonce free ... and she sashayed away from the devil equipment. After the show, Beyonce posted a poetic note to her fans explaining the situation...