@ gregorimendel,
You have responded to a thread that is 8+ months old. Can you please open up a new thread so we can help you?
In your new thread, please let us know what version and product of Avast you are using (example Avast Free version 6.0.136x). Also include information about your machine (example Windows, 7, Vista, XP, and the SP), security programs you are using and any other information that will help us. Thank you.