I am not sure if this might be the cause of your problem; there is a note in Microsoft Office Online - Add a user role, and I quote "If you assigned groups of users to a user role, users belonging to that group must be online for the user role assignment to take effect. If a user is working offline, InfoPath uses the default user role to open the form."
here is the URL for that article if you are interested in reading it:
http://office.microsoft.com/en-ca/assistance/HP011066061033.aspx
Stephanie Cantwell / Test ManagerQdabra® Software / Streamline data gathering to turn process into knowledge