Safari did not redirect to protected page

[Qian, Yi]

Hello,

During testing setup Library SP federated with our IdP, Safari stopped at
the URL https://test.lib.ku.edu/Shibboleth.sso/SAML2/POST with following
error message   

    "opensaml::BindingException at
(https://test.lib.ku.edu/Shibboleth.sso/SAML2/POST)
     Invalid HTTP method (GET)."

Other browser (Chrome, FF, IE9) will redirect user to correct page.

Could someone tell me how to nail down the cause?

IdP is shib 2.3.8, SP is shib 2.1.1

Yi