A 2007 sexual assault case is coming back to haunt Carl Stanley McGee, the new acting director of the state gambling commission, after McGee’s former boss claimed that McGee was a victim of a “false accusation’’ in the alleged encounter with a 15-year-old boy. To support their claim of a sexual assault in a hotel steam room, the boy’s family released the results of a 2008 investigation by Florida child welfare officials recommending that McGee be prosecuted.