Getting an error message when trying to preview a post

I seem to be having strange error messages after installing the domain mapping plugin. One of them is that a subsite that installed the domain mapping plugin is getting this message when clicking on the preview button:

You do not have permission to preview drafts.

Even when I log in as the super admin to their dashboard, I get the message.

Any ideas when this is happening?

I know I need to try a different Cache plugin because mine (Quick Cache) is not compatible with Domain Mapping plugin, but I don't know if this cache plugin would cause this "You do not have permission to preview drafts" message.

Thanks, Joe.