This seems weird, but maybe on user has access to a list generated from an external file (such as an XML file or SharePoint list) and the other doesn't. This is all I can think of. However, the only way this will happen is if you are doing explicit referencing (instead of looping through all of the elements).
I hope this helps, but I think we need a little more info to provide more specific advice.
Matt Faus / Microsoft InfoPath MVPQdabra® Software / Streamline data gathering to turn process into knowledge