Google has made some recent changes in Google Apps For Education, Business, and Government. The "Sharing Settings" in the administrative control panel now affect secondary and resource calendars as well as primary calendars. If there is a secondary calendar embedded in a site, you may need to modify the settings to ensure that the calendar is still visible or has the sharing settings you chose.
You can read more in "Set Calendar Sharing Options," http://support.google.com/a/bin/answer.py?hl=en&answer=60765&topic=9201&ctx=topic
Or, download the attached PDF file at the end of this post.
Google Apps For Education K-12 Regional Leader