Hi James,
thanks for the quick reply, I am using the latest version of the plugin 0.7.2,
I found out that if we do not have menu set in the back end and debug is open, we have the errors, again it is fresh WordPress installation only with your plugin
to solve the issue, I just created menu in the back-end and it worked
I suggest to add condition in the code for that so it will not raise errors if no menus are defined.