On September 27, 1999, about 1530 eastern daylight time, a Boeing 767-332, N196DN, registered to and operated by Delta Air lines Inc., as DAL147, had a flight attendant sustain an injury while on a Title 14 CFR Part 121 scheduled international passenger flight from Vienna, Austria, to Atlanta, Georgia. Visual meteorological conditions prevailed in the area at the time, and an instrument flight rules flight plan was filed. The airline transport-rated pilot, first officer, reserve pilot, 8 flight attendants, and 199 passengers were not injured, but 1 flight attendant received a serious injury. The flight originated from Vienna, the same day, about 1115. The flightcrew stated that as they made the descent into the Atlanta area, they were on the Macey arrival with a clearance to cross Logan at 12,000 feet, and had asked air traffic control (ATC) for, and had received approval to deviate to avoid numerous cloud buildups. The aircraft was heading 227 degrees, and the flight was being seqenced for runway 08, when the north arrivals controller told them that they would be switched to the south runway, and to contact the approach controller on 127.9. When the crew contacted the approach controller, they informed the controller that they were leveling at 12,000 feet, and the controller told them to turn to 180 degrees as soon as able. The approach controller told them shortly thereafter that traffic was at 11,000 feet. The crew noted the traffic on the TCAS, and that the traffic was climbing out of 11,000 feet and rapidly approaching their altitude. The captain, the pilot flying, had begun the turn to a heading of 180 degrees requested by the controller, when they received a traffic advisory from the TCAS system, followed by the dot on the TCAS screen changing color to yellow. While in the turn, the captain disconnecting the autopilot to make a quicker turn to get away from the traffic, and as the autopilot disconnected, the airplane pitched up and climbed about 200 feet. A flight attendant in the aft end of the airplane sustained a serious injury during the maneuver. The flight crew never received a resolution advisory from the TCAS, and never saw the traffic since they were in the clouds at the time. The seat belt sign had been on for some time previously, and the no smoking light had been cycled due to weather. A review of the FAA transcript of communications revealed that at 1902:31 the Atlanta Approach Terminal Arrival - H (TARH) controller stated to DAL147 that the northbound traffic would be leveling at 11,000 feet. At 1902:37 DAL147 responded saying that they had the traffic, and the TAR-H controller then instructed DAL147 to maintain visual separation. This instruction from TARH was given to DAL147 while the flight was in the clouds. At 1902:43 DAL147 said "okay he's *(fourteen) he's on icas showing (garbled) turn right turn right." At 1903:12 DAL147 said to TARH, "...i thought you said he was at eleven." At 1903:18 TARH replied saying, "...I thought they had stopped him at eleven." The FAA transcript of communications also revealed that at 1901:46 the traffic, a Continental Airlines flight (COA66), was climbing in the clouds, and had been cleared to 14,000 feet by Atlanta Departure Control (DRN).