http://avherald.com/h?article=43fafdd9
Incident: Air Canada B763 near Dublin on Jul 14th 2011, pressurization problems
An Air Canada Boeing 767-300, registration C-GHPE performing flight AC-895 from Dublin (Ireland) to Toronto,ON (Canada) with 234 passengers, was climbing through FL160 towards FL260 when the crew requested to level off at FL170. The crew donned their oxygen masks, reported pressurization problems and requested to return to Dublin. The airplane descended to FL080 and landed safely on Dublin's runway 28 about 25 minutes later.
The flight was cancelled.
While taxiing in the crew requested a ground air starter unit to be available due to inoperative APU.
The airline said a pressurization indicator light illuminated shortly after takeoff. Passenger oxygen masks did not deploy. The flight is now estimated to depart the following day (Jul 15th).