eBS 11i: Issues with the attachment in the application

Hi!
  We are facing an issue in a 11i instance of eBS, and I'm not geting in the right direction to analyze and solve the problem.

Instance:
Oracle eBS 11i
Linux x86

The issue is like this:
You are in a form that has the option to attach a file, the form to attach a file is open, and when you select the "Data Type" as "File", automaticly I get a generic error of "your session is no longuer valid.". (Of course the session is valid and I can continue to use the instance normaly, the error is only when you try to attach a file.)