If at all possible you should try to not store objects in the session. It is messy, and tracking down related bugs is not fun.

Consider storing the key for your item in the session, and the retrieving it from the database again next page load.

You may also wish to check if adding an explicit use Application::Foo::Bar at the top of your script helps, it is entirely possible that the Apache process that is failing has never compiled Application::Foo::Bar, and that is why it is complaining about there being no ID method.