On your SharePoint 2013 Preview environment, there may be times when you log in as different users and get this error:
“The context has expired and can no longer be used. (Exception from HRESULT: 0x80090317)”
This is the same error that would be thrown in SharePoint 2010.
Take a look at making sure the time zone and the correct time is in sync with all your servers first and then do an IISReset. Seemed to solve it for me