Hello,
In order to diagnose why this is happening can you please do the following :
1. Confirm that you are using the latest version of the Ai1EC (2.0.13) - If not, please do a manual upgrade: http://support.time.ly/manually-upgrading-the-calendar/
2. Check to see if you are experiencing a theme or plugin conflict: http://support.time.ly/do-i-have-a-theme-or-plugin-conflict/
Please let me know how this goes.
Thanks