More problems for the troubled Criterion Theatre. Westminster City Council have refused to allow the American comedy act The Flying Karamazov Brothers to juggle with chainsaws. 'We can't guarantee the safety of the performers, which is our legal obligation,' said a council spokeswoman, despite the immense popularity of the routine. The council will meet again next Thursday to reconsider. Meantime, the Brothers will juggle knives, swords and scythes . . .