Ultimate Facebook Plugin: 404 page error served to user after they log in.

After a user logs into my site through the Ultimate Facebook plugin they are directed to a 404 error page.

The URL that is shown in my browser is example.com" target="_blank">http://example.com/httpexample.com

If the user navigates back to another page in my site everything is fine and they are logged into my site. Its that first page they get served that is asking to be slapped

Any thoughts???