Logged out when hit home link in drupal 7.19? Noticed I am auto logged out or at least that is how it appears with the admin bar disappearing and login form visible when I hit the home link.

If I go from logged out home page to another page I appear logged back in.

I am on drupal 7.19 and it resides in a folder set up as a subdirectory.

drupal.mysite.com

the folder is at drupal.mysite.com/drupal

This only occurs when I am navigating about without www prefix and does NOT happen when navigating about with www prefix. My site can be accessed either way but currently advertising as without prefix. The www is more secure obviously but need both to work.
Answer is well stated here http://drupal.org/node/110478

Had I spent a little more time reading I would not have had to ask this question.
Also I can see now it is making it so no matter which prefix you use the cookie will stick.