If you're like me and tend to get lazy with typing the whole URL in your Firefox browser so it just takes you to the first result automatically, you'd notice that OpenDNS has overridden that feature by default.
Instead of letting Firefox take you to the Google search page, it will take you to an OpenDNS Guides page such as http://guide.opendns.com/?url=search+query
To disable this, open up the OpenDNS dashboard to configure the advanced settings.
Untick everything on this page and it will work, although I believe the main culprit is "Enable OpenDNS proxy".
I still have "Enable stats and logs" enabled, but unsure whether this still works or not.