InfoPath Dev

I have created an expense site using the pre-defined Expenses SharePoint template in WSS 3.0 which contains the InfoPath Template "ExpenseForms/Forms/expenser.xsn".  This is working fine for myself and a colleague, however when a third colleague (who also has InfoPath on his machine) tries to create a new item or edit an existing item in the library, he gets an error message - "InfoPath cannot open the following file <file details>". 

I saved a copy of the form I wanted him to view locally and emailed it to him using Outlook, however when he tried to open the emailed form he got another error message - " InfoPath cannot open the following file <file details> The following form template for the form cannot be found <template details>".

Has anyone else come across this, or does anyone know how to resolve this so that my colleague can access this form?

Many Thanks.

Here is the basic architecture of InfoPath.

A template ).xsn) file is created with InfoPath designer.

This must be published to a central location and all form user must have access to it.

Since each form that is created or opened must reference the template.  XML documents only contain the raw data, the template stores the rendering, logic, and display instructions. 

If your friend gets an XML document, it will attempt to open the template inorder to open the form, if it cannot find the template you get the erro you list.

For the other one he probably does not have the correct Internet Security settings for the site or lacks the correct permissions.  InfoPath use Internet secuity and the site should be in the trusted or local intranet zone.