man.. i really think there is security issues.
check your owa security settings like the first response I sent you... I know you mentioned that they are the same, but I'm thinking there is parts that aren't.
on the security stuff, check something and then un-check it to force it to re-apply....
such as give the default website basic authentication and then uncheck it and then apply it.
on some of the virtuals it's gonna ask you to apply to the child also, and pick all the child and let it apply.
then iisreset again