Thought this could prove useful for some of us... This morning I found that the OWA access was broken. Getting an Error 405 "http verb used is not allowed"...after I logged into OWA. I flushed the temp cache for IIS and then restarted IIS...did not solve it. I disabled Forms Authentication on the IIS server - restarted IIS - then reapplied the Forms Authentication and got it working.