I have a tricky security issue that i could use some help with.  I
have an InfoPath form that is saved on a SharePoint site.  The code
behind the form is written in VB, using Visual Studio 2003.

To determine the user's ID it uses the Environment variable, the code
also sends email (not sure if any of this is relevant but i thought
i'd mention it).

Everything works fine for all the users that belong to our
organization.  However, now i need to allow a user from another
organization in.  The user can sign on to SharePoint, but when  he
tries to open the InfoPath form he gets the following error:

"Your user name or group membership cannot be verified because the
form's security settings do not permit it."

Can anybody provide some guidance?

thanks!