Honestly, I would delete the form and try recreating the form using the wizard again. If all works before you make any custom changes than you know it is your tampering that is failing the page.
Thanks AquaNX4 for reply, but I do not believe that is a way to handle problems. There is a reason for the error of course.
Sometimes it is, but I wouldn't pull the plug on this case just yet ;p
Check the primary key column/item definition in the Automatic Row Fetch process. Then check the parameter you passed to the page.
I'm going to guess that the process references P4_ROWID, while you've passed the data in the APEX URL using P4_ORDER_ID.
Your exact form definition is unclear, so if you need more detail you might need to provide some page designer screenshots, or mock up an example.