Devondale Skim Milk Problem

One of the Devondale Skim Milk 200ml Tera Brik cartons I purchased has swelled up like a balloon. It appears likely that milk is contaminated. As the container is still sealed, this appears to be a manufacturing problem, but has only occurred in one out of six of the UHT cartons purchased. Has anyone else had this problem? The carton is marked "29 APR 2010 G210 16:09 REG NO 1029".