I upgraded to the latest version of wp then installed this plugin.
Tried to add a test a event. Got this error
There was an error updating event details. Date and time of completion of the event can not exceed the date of its beginning, please try again.
I made the adjustment and then got this error:
There was an error saving event details, please try again 
If I want to set an event for 2/28/2011 at 9pm to 3/1/2011 at 3 am