After trying to use this combination on a site I was building for a client (I am a designer, not a programmer), I can get the events to save to the calendar in the back end, but the calendar shows no events. This is on a clean install, r108 of Event Calendar and r395 of DataObjectManager.
There are no other modules, and it is using the default theme (I was trying to see if it was my custom page types causing a conflict - it isn't them, because they aren't there).
There are no errors, nothing. Just no events in the upcoming events (or on the calendar).