A qRules user couldn’t open the qRules full trust form for mapping to lists on his computer after installing – he was getting this error:
InfoPath cannot open form "Form template: file:///C:\Program%20Files%20(x86)\Qdabra%20Software\Qdabra%20Rules%20Library%20(Trial%20Version)\Forms\Qdabra%20InfoPath%20to%20SharePoint%20List%20Tool.xsn The form template cannot be opened, because the system administrator has disabled opening form templates that require full trust."
He resolved this as follows -
Open InfoPath Filler > Form Options > Trust Center > Trust Center Settings > tick "Allow fully trusted forms to run on my computer"
Raise your hand if you didn't know about this setting - I didn't! :-)