I am seeing the following errors when reviewing your plugin for a client.
Notice: Undefined index: qunit in /Users/bushaw/Sites/wpclients/wp-content/plugins/editorial-calendar/edcal.php on line 488
Notice: Undefined index: post_type in /Users/bushaw/Sites/wpclients/wp-content/plugins/editorial-calendar/edcal.php on line 628
Try using isset() to verify your $_GETs first.
Also, after enabling this on my local install (running as multisite) this was not working. The red error box shows up immediately with no message and the days show up with undefined in the title. Screenshot here: http://cl.ly/1H1p153w3w3B1623312f