Help: Why does Calendar 7.0 deletes details of new event just after entering?

Just after I create a new event on Calendar and "saving" (i.e., clicking out of the event), I see the event as I typed it. Then within a handful of seconds the name of the event reverts to "New Event" and all information entered is wiped away. I then open the new event, reenter the data, click out of the event and all is fine.

Frustrating to have to enter an appointment twice to get it to stick. Anyone have ideas as to what is going on and how to fix the problem?

I am running OS X 10.9.5. I sync Calendar through iCal to 2 other devices an iPhone 5 (running current iOS) and a Mac (running OSX 10.7.5). On this mac, I have iCloud set to Refresh calendars manually (which I used to have set to "Push" but have been experimenting with this field to determine if it is the source of the problem)