FYI to others with this issue. The problem is now fixed.
When I looked at the code and ran some tests for some reason the form variables for the login form was empty. The post variables were not being passed. After some research I found this post which explained the issue:
It appears that a redirect was added at some point to the web server to redirect the domain from
This combined with the incorrect Geeklog configuration values for site_url and site_admin_url which was missing the "www." part in the domain caused the issue.
Remember when changing the domain name at all you should run the Geeklog install script again (for the version of Geeklog you have installed) and then select the Migrate option. This will update all the configuration variables needed.
One of the Geeklog Core Developers.