By Karolos Grohmann RIO DE JANEIRO, Aug 6 (Reuters) - The Rio de Janeiro Olympics got off to a shambolic start on Saturday with fans queuing for hours to enter the stadium and some missing their events as many athletes competed in front of eerily empty stands. Games organisers apologised for dropping the ball on the first day of full competition, the morning after a dazzling opening ceremony, as iconic venues such as beach volleyball on the famed Copacabana beach saw only a few hundred spectators. "Indeed we have problems in some (security checkpoints) in the Olympic Park and we apologise for everybody standing in line outside the venues," Games spokesman Mario Andrada told reporters. More...