"Getimagesize" error blocking wp-admin access

Hello.

When I try to log into my Wordpress Multisite: http://myxtremewebsite.com/wp-admin/ I get this error:

Warning: getimagesize(http://myxtremewebsite.com/wp-admin/images/wordpress-logo.svg) [function.getimagesize]: failed to open stream: Connection timed out in /home/myxtreme/public_html/wp-content/plugins/ultimate-branding/ultimate-branding-files/modules/login-image.php on line 121

I see it has something to do with the ultimate branding plugin. Please explain why this happened and how to fix it. All the sites on the Multisite show fine, however I can't log in!

Thanks