I was developing using DayPilotProTrial-3.8.1075 and I used a javascript confirm on the delete event as described in: http://forums.daypilot.org/Topic.aspx/78/deletion_of_events .

EventDeleteHandling="JavaScript"
EventDeleteJavaScript="if (confirm('Do you really want to delete ' + e.text() + ' ?')){ dpc1.eventDeleteCallBack(e);}" OnEventDelete="DayPilotCalendar1_EventDelete"

That worked just fine.

Today I've replaced the trial with release version 3.8.1086 and the javascript call to the callback event seems to be broken. The confirmation popup is shown, but the server side event handler is never called.

If I replace the dll with the trial version (and change nothing else) it works again. If I change the EvenDeleteHandling to CallBack it works fine as well in the release version (obviously w/o the confirmation).