SGC and Events Calendar Pro conflict causing the backend of WordPress to break. This problem is only with the Pro version of Events Calendar (latest version of SGC) I spoke with support from Events Calendar and they would give you a licence if you are able to work together to find the conflict. Simple Google connect seems to cause the same or similar conflict. Here's a link to the original Forum post over at Events Calendar forum: http://tri.be/support/forums/topic/activating-pro-2-0-2-breaks-backend/
I also discovered that SFC breaks Events Calendar Pro's iCal function. I can't figure out why that would cause a conflict.