As told you on email that this is caching error .
Hi this is caching issue .The page is being cached into browser .It seems like you or your host has implemented the page caching into your site pages .
You need to clear all caches and disable the caching (contact webhost on this) .
Please disable the caching for logged in users .
The only solution is to contact your webhost clear up all your cache and disable all kinds of cahes .
check your .htaccess file for caching rules . You webhost can help in this .
This is not theme issue , if you use any theme with login capability you will see this error .