The reason you are logged out when you access it without the www. subdomain is because the server treats it differently. Or rather, the cookies do.
As such, I'd recommend you either force www or non-www upon your domain. It should also prevent duplicate content from showing up and being sent to Google. Open .htaccess or create it and add the following if you want to force www.
Code:
RewriteEngine on
RewriteCond %{HTTP_HOST} ^yourdomainhere\.com [NC]
RewriteRule (.*) http://www.yourdomainhere.com/$1 [R=301,L]
Or non-www:
Code:
RewriteEngine on
RewriteCond %{HTTP_HOST} ^www\.yourdomainhere\.com [NC]
RewriteRule (.*) http://yourdomainhere.com/$1 [R=301,L]
Replace it with your current domain name. That should get rid of your issue.