I posted this on the wordpress.org support forum.
As I said there.
Due to the way that the session is started in this plugin it interferes with any session values set in any other plugin.
I come to this conclusion because the only other plugin that deals with session on the site where I am having a problem is this one.
I believe that the correct way to start a session is not at the top of the plugin but by calling a function on init.
I posted an example of the code I use for starting a session and running scripts that require sessions over there, it does not appear that I can post code here.
http://wordpress.org/support/topic/any-mobile-theme-switcher-interferes-with-session-values-in-other-plugins
The problem is that the session values from my plugins that required them are destroyed by WordPress if they exist when the function wp_unregister_GLOBALS() is run or some other function. There’s a decent post about it here http://