InfoPath Dev

 I created a new form with InfoPath 2013, published to a SharePoint 2013 site.  Open in the client application.  Got this when tried to open:

Form template: /Forms/template.xsn
The form template was created with a newer version of InfoPath.  This form template was created by InfoPath version 15.0.0.

Well - if you created an InfoPath 2013 form and are trying to open it with an earlier version of InfoPath, you'd get this... but it sounds like you created the form with InfoPath 2013 and are opening it in InfoPath 2013... You can always open the form in design mode again and change the compatibility under File > Form Options > Compatibility. Try setting it to InfoPath 2010 and republishing? You may need to remove the form that won't open from your cache - you can open InfoPath Filler, go to New, find the form, right click and select Remove (or try getting an update after you've published).