Googlebot Error 403 – Time.ly Calendar

Hi

I have a somewhat strange problem

When I activate the Better WP Security Plugin, the Googlebot can not access the calendar data from the plugin Time.ly Calendar. Google will get to see only the 403 error page.
But when I call the calendar data from the browser, I access it without any problems.
An example URL: http://www.milizfeuerwehr.ch/ai1ec_event/knabenschiessen-2013/?instance_id =

What can I do to Googlebot also get access to the site?

Sorry for my bad english.

http://ww.wp.xz.cn/extend/plugins/better-wp-security/