CalendarExtender Not Working

I haven't read about this anywhere, but the CalendarExtender hasn't been working for me for some time.

I keep getting the following javascript error when i attempt to Pop it up:

Sys.ArgumentNullException:Value cannot be null. Parameter name: classNameI just picked up 14100 off of CodePlex and can confirm the same thing with the development branch.
As far as i can tell this began happening after the 11645 changes
There is a calendarextender?