Question on a Workflow Application Error

An end-user received this error message when they tried opening a form that was assigned to them.

I looked up this error in the User Portal and Process Design and Administration support manuals and did not see it listed there. Can you please provide me with the cause of the error? Thank you in advance. We are using version 7.18.2.

I received this error a while back.
For me, the error occurred when attaching a file with a filename that was too long.
It didn’t error when the file was being attached, but did error after submitting the form.
Maybe the cause is the same for you?