Don’t assume both sites have access to the same form…
Please check and make sure that both sites have installed and activated the formidable plugin.
Check if both sites have a form 2.
I have installed the plugin on both sites separately, and both forms have an id of 2.
Do both sites use the same plugins?
If not: Rename the ‘different’ plugins of the ‘broken site’ by putting a ‘0’ in front, and check if the problem goes away.
If the form looks correct in preview mode where files from other plugins and your theme are not loaded, it would point to some kind of conflict being caused by one of your other plugins or your theme. I would start by deactivating your other plugins and theme one at a time to see if you can find where the conflict is.
If you would like to create a new topic on our helpdesk on FormidablePro.com, we can be of further assistance.