If you are using my Drop in replacement for V and NV function and you are upgrading to Oracle APEX 3.1 then you have to alter the functions to reference the new schema FLOWS_030100!!!
If you are not doing this your applications will not work because the functions are trying to read the session state from the old FLOWS_030000 schema, but there no values can be found for the current session which are stored in FLOWS_030100.
Just to let you know that you are not searching to long why your application doesn’t work after the upgrade.
Note: You may have installed this drop in replacements as optional part of the ApexLib Framework!