Just pushed a 2nd update to Beta 3. This Update 2 (aka 3.0.0_M4_62) has a bug fix for the calendar. The last release had a bug where if you edited an event that had attnedees the event was lost/moved for all attendees.
You can get this from Sourceforge (OSS builds):
http://sourceforge.net/project/showf...roup_id=153217
Or from the support portal for Network trials and customers:
http://www.zimbra.com/support