This leads me to believe the problem isn't related to any of those issues.
Why? Your diagnosis of the problem so far has been "completely white page loads". No mention of HTTP header, content ... for all you know both machines have the same (or similarly) faulty firewall, have the same virus, go through the same faulty node (or multiple faulty nodes) on the network... unless you can diagnose it using your web servers diagnostic facilities (log analysis), and your browser, you can't rule out anything :)