This error occurs when a conditional statement is not set up correctly.  Opening a template using the Visual Editor will strip conditionals and is the most common cause of this error.

Open the affected template using the Source view and check for incomplete conditonal tags.  They will look like this:
<t:if>

There are no backups or versions of the templates, so you'll need to check your other templates (also using Source view!) to determine what the proper conditional should be.  Two common statements are:
  • <t:if test="isMobileSession()">
  • <t:if test="!isNull">
Please keep in mind that Luminate Support does not troubleshoot issues with custom content, so if you encounter any problems, then you can try getting help on our community forums.