Do you know the URL to which Firefox is trying and failing to connect? If so, could you load it in a different Firefox tab and check the "Technical Detail" section of the page for more information?

Firefox 31 introduced a stricter SSL component, and some sites that use self-signed certificates are no longer allowed (according to a post earlier today). There is an insecure workaround for this, but it is not recommended for long term use.

See: Security certificate no longer valid after upgrading to latest FF.

Is that relevant to your application?

The 2nd url is proxied by the vcloud server and is accessed only as a redirect. It cannot be accessed directly. When I capture IE traffic, i can see treffic from the second IP. FF never attempts to talk to the second IP.

We are not using self signed certs...

I don't think I have enough experience with proxy servers to suggest how you might get a peek at the certificate in Firefox.

Does Firefox 31 object to loading any other secure sites through the proxy or is it just the one?