Getting 404 URL Error

Hi,

I am using the following test calendar – https://www.google.com/calendar/embed?src=8fl8gi67pcu8f8tvtp13t8j4bg%40group.calendar.google.com&ctz=Europe/London with your plugin but the widget is giving a 404 URL Error.

The above URL works without me logged into Google Calendar so I am positive that is correct – additionally I have put an embedded link on another page and it displays correctly.

I am at a loss at why this is happening, I have tried every option in the settings and widget including a refresh but nothing works.

Any thoughts or pointers would be useful

http://wordpress.org/extend/plugins/google-calendar-widget/