I have noticed on my past few flights that I am consistently getting a cabin pressurization failure above FL300 (more or less). At lower altitudes the pressurization functions, though it does not seem to pressurize the cabin at an expected value - the cabin altitude seems to be higher than expected at a given altitude, and the cabin pressure altitude discrepancy increases as the aircraft altitude increases. At altitudes above FL300, the pressurization eventually just gives up and the cabin depressurizes completely.
Am I missing some pressurization procedure setup prior to takeoff? The pressurization system seems to default to auto settings initially, so I do not change them. Also, the FMC gives a cruise altitude above max flight level message at FL360 - isn't the A300 rated to FL400 for cruise?