Created attachment 67349 [details]
Note: all instances of the same birthday are highlighted when I click only at one of them

Version:           0.9
OS:                Linux

I accidently imported the same addressbook twice. After this the birthdays by same users were shown multiple times (BUT are behaving like one entity: please see screenshot). Also after removing one copy of the addressbooks, all copies of the birthday event are still visible at the calendar.

Reproducible: Always

Steps to Reproduce:
The easiest way is: 
1. import an addressbook that contains birthdays (I am using the groupdav resource) with egroupware
2. go to akonadi console and clone the resource (give it a new name and by this trigger synchronization)
3. the birthday is show two times.

Actual Results:  
the same event is shown multiple times AND it is not possible to delete it

Expected Results:  
show only one event

OS: Linux (i686) release 3.0.0-1-686-pae
Compiler: gcc