I am having this same problem.
WordPress version: 3.5.1
It happens right after I Install & Activate the plugin.
My error says, “The plugin generated 158 characters of unexpected output during activation. If you notice “headers already sent” messages, problems with syndication feeds or other issues, try deactivating or removing this plugin.”
Yes, I too am getting duplicate meta title tags when I activate this plugin. I’m running WP 3.5
