Has anyone seen after a user migration from Exchange 2003 to Exchange 2010 user who are unable to access OWA? Using Chrome you can see a 301 redirect loop when hitting the languages page. I can manually force language selection, but then users cannot complete any actions with their mailbox. There is nothing in the CAS server log files indicating issues with the server or account. I have completely torn down and rebuilt the virtual directories, but still have the same issue. My 2010 CAS servers are Windows 2008 R2, Exchange 2010 SP3 RU3.
Often people setup HTTP Redirect incorrectly on the root and it breaks /OWA sub paths. You can setup redirect, BUT you have to make sure it only takes affect for root and not sub paths. Google is your friend.