Since yesterday, some Avira Internet Security users have only been able to use their web browsers if they first disable Avira Web Protection. According to Avira, some customers are getting a “data structure error” that requires a complete uninstall and fresh installation of the program.
However, users in the Avira forum are saying that reinstalling does not solve all their problems: activating IPv6 support and the Drive-by protection causes new browsing issues – this appears to be a Java-related problem, particularly if the latest version, Java 7, is installed. Disabling browser protection is the only way to get around the problem. Chrome, Opera, Firefox and the Thunderbird email client are all affected. Avira has acknowledged that there is an issue with Avira Web Protection and the recently released Chrome version 28; the problem is currently being investigated.
The cause of the problem is not known, but may have been the result of a regular signature update. The recently announced forced upgrade of 2010 and 2012 versions to the 2013 version seems to be unrelated.
Source: H-Online
Update 1:
There are a temporary fix for now: http://www.avira.com/en/support-for-home-knowledgebase-detail?kbid=1500