InfoPath Dev

I have a form that is read only on the infopath form depending on the users group. A non admin can create a new document and submit it to my sharepoint 2010 document library. (I'm using Infopath 2010) However, when the admin updates the form to enter a value in the read only field (which is a people picker) The non admin can no longer ...

Hi - I am brand new to InfoPath (which is why I am posting in the shallow end of the pool)  I purchased a book and one of the examples showed how to change the ID field to concat "ID" with the current date/time.   However, after I implemented this, I am getting the error, "Only positive Integers ...