Similiar event happened to me on a Qatar Airways flight from DOH to FRA a few years ago over Turkey. The plane suddenly pitched to one side without warning and us lot down the back sent our juice trays flying. The Captain was quick to make a PA to reassure everyone and it transpired that a 747 ahead was climbing too slowly and we got too close to its wake vortex or something to that effect. The Captain later told me that this was the closest he had ever gotten!!! lol