[Plugin: Google Calendar Widget] No events displayed

Hi,
I really like this plugin although i just can’t get it to work? :/
It works fine with the google dev calendar which is being displayed correctly but it seem impossible to get it to display events from any of my own google calendars that I have tried to connect. I even created an empty one for test purposes with just one event today and neither that works.
Am I doing something wrong or have I missed something? Could you please give me a hint?

Here is the test calendar I use:
https://www.google.com/calendar/feeds/g3hrfr14d790unpng5jp1sv78s%40group.calendar.google.com/public/full

Thanks a lot!
BR Daniel

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