http://avherald.com/h?article=41ab51bd

An Air Canada Airbus A330-300, registration C-GFAF performing flight AC-3 from Vancouver,BC (Canada) to Tokyo Narita (Japan) with 147 people on board, had departed runway 26L and was climbing to cruise level, when the airplane levelled off at FL260 due to pressurization problems. After some troubleshooting the crew decided to return to Vancouver, where the airplane landed safely on runway 26L about 65 minutes after departure.