Exchange 2010 OWA: An unexpected error occurred and your request couldn’t be handled

If you receive this error after installing Exchange 2010 service pack you might want to delete any custom bindings on your Default Web Site in IIS.

To do this open IIS Manager, expand your server->sites and select Default Web Site, right click it and  choose Edit Bindings... Remove any custom headers you added and it should work right away.

Links:

http://jaxelos.wordpress.com/2011/12/01/owa-2010-an-unexpected-error-occurred-and-your-request-couldnt-be-handled/