Receiving the following error: “The form template has been published to the server but it can only be opened in InfoPath Filler. The sandboxed solution could not be activated. The custom code in the form cannot be run. This functionality may be deactivated on the server. For more information, contact the server farm administrator.”?
First, ensure that you’re not doing something legitimately wrong by designing a new form and publishing it to a form library successfully. Then prove the negative case by adding some code, such as an empty event handler. If the publish gives you the error described, and you’re trying to deploy to a SharePoint server that is also a Domain Controller (common with development and/or investigative Proof of Concept VMs), then try the registry permission fixes described in the following KB: http://support.microsoft.com/kb/2026191. Worked like a charm for me.