TOKYO - The Japanese distributor of “Babel” is warning audiences the movie may cause nausea or headaches. Gaga Communications has received 15 complaints since the film, starring Brad Pitt and Cate Blanchett, opened Saturday in theaters throughout the country, company spokeswoman Aimi Ichikawa said Wednesday. Ichikawa said the company was investigating which scenes caused the illnesses, and hasn’t ordered theaters to adjust sound or lighting.