multiplying entries in outlook group calendar

[hansjuergen.riess at t-online.de]

I created a group account in Kolab and a file <group>.pst for each user.
This pst-file was connected to this group in Kolab via Toltec Connector 

in XML-format.
All worked fine for a few weeks, but then entries within the group
calendar
were multiplied. I thought of a mistake of mine and deleted all
pst-files
and the group account. All was set up new but after while the entries 
were multiplied again.
What is the reason for this and is there a script to delete the
multiplied
entries ?
Any hints to solve this problem ?

Thanks in advance