InfoPath Dev

I have built out the vlookup functionality in an InfoPath form referening a secondary source located in a sharepoint list which is filtered depending on the specific form that is open.  I used information in  http://www.bizsupportonline.net/infopath2007/how-to-vlookup-infopath-look-up-data-sharepoint-list-rules-filters.htm  and ...

 I recently added User Role functionality to a form created in 2007 but saved in the compatible version for 2003 and it is working as expected for most End-users (whether 2007 or 2003).    However, I have some End-users (in 2003) that recieve an error when they try to open the file that states: InfoPath cannot open ...