The widget does not show posts from Google +1. Instead it tries to show posts from Google Buzz. It also only does this if the statistics option is enabled, otherwise it shows a blank area.
This is the same on the plugin demo page
Looking at the page source this error message appears "div class="tab-plusone tab-inner"><!--Error: Google Plus did not respond. Please wait a few minutes and refresh this page.--"
Have checked this on several occasions...
Still using the plug-in on SME Technology Facebook and Twitter work fine.