Hi Heiko,
The message you are getting is default, every time displayed above the search list, if you given
Maximum search list =10, then you may get the message More than 10 incident found.
I suppose this is the very regular behavior.
Check Enterprise search in SAP CRM Enhancement Package 3 (CRM 7.03) - CRM - SCN Wiki
Check question
2.2 Maximum Number of Results set to 100 and Maximum Number of Results set to 10
Thanks
Jansi