Follow up to this:
http://stackoverflow.com/questions/795414/why-cant-i-pass-user-sessions-between-subdomains
I followed the advice there and used :
ini_set('session.cookie_domain','mydomain'); (with and without a dot before mydomain) as the first line of index.php in the public folder as advised there and in other links around the web. The problem is that it completely "ruined" Zend_Session_Namespace inside my application. While it persisted among calls (as it should) of the page, now every time it is being called it is behaving as a new session is being instantiated, without holding all variables. Any ideas on how to fix this?