Avira Free Antivirus for Mac does not work anymore after you have upgraded your system to Apple 10.8 "Mountain Lion" without applying the latest patch03 first.
This is due to changes within the system structure of the Apple OS. Some folders will be removed during the upgrade that are usually needed by your Avira installation.
If you read this article before you have upgraded to version 10.8, we strongly recommend to apply our latest patch03 to fix this issue.
For instructions on how to apply the patch to your Avira Free Mac Security installation, please read this article.
Otherwise you will have to remove your current installation, download the installation package from our website and reinstall it.
Once completed, your Avira Free Antivirus for Mac should work again.