OWA session timed out - SBS 2008

OWA - gives following error

"Your session has timed out. To protect your account from unauthorized access, Outlook Web Access automatically closes its connection to your mailbox after a period of inactivity. Please re-enter your user name and password. "

Try following

Confirm the Authentication on the IIS Virtual directories as below

Default Web Site -> Anonymous Authentication Only.

OWA -> Basic Authentication Only.

Try and disable Form Based Authentication (Enable Basic authentication from EMC) and then test OWA and confirm if your session still gets timed out.

Try Disabling Thrid party AV 

Reference (http://www.experts-exchange.com/Software/Server_Software/Email_Servers/Exchange/Q_24506810.html)