Did you try asking the user to clear their InfoPath cache? Perhaps this is a template issue of some kind and clearing the cache might resolve the issue.
1. Close all instances of InfoPath on your computer.
2. Click on the Start button in the lower left hand corner of your computer and type in Run.
3. Open the Run application.
4. Copy the following and paste this in the the Open: text box in the Run application: infopath /cache clearall.
5. Click OK.
Ted