Cannot call method '_preInitialize' of undefined on Events in calendar view
I have a site that was using the calendar view for events. I upgraded it from 6.0 to 6.1 last week and all seemed to be running fine until I went to edit the calendar and noticed the page edit screen was not working. I am seeing this error in Chrome devtools "Cannot call method '_preInitialize' of undefined" and then an error for a missing resource 404 on webresource.axd<really long guid type string here>
Visually the calendar looks fine, but the actual edit/more button on the widget itself are gone and the page edit tools only show the more actions button. (so missing publish, draft, preview). I normally see this when there are script errors so that is what prompted me to dig.
I had to revert my widget template for calendar view back to the default and it became a happy camper.