Ive noticed this when behind a corporate firewall. If I swap to a 'public' wifi all is good. There are potentially a couple of reasons when behind a corporate firewall;
The corporation firewall breaks open the SSL session and dynamically generates a certificate. This works when the corporaten's root CA is installed in the browser, however often the JVM certificate store is overlooked.
The firewall does content inspection and just refuses to let the content through when the user agent is not a recognised browser...