Hi,
I saw a similar problem in your forum but unfortunately there wasn't any resolution. So posting it again.
I am using Avira free antivirus without webguard. Today I installed Online Armor free firewall but Avira seems to have this problem. The control center opens in windows classic mode. Fine thats not a big problem. But even some functionality seems to break, such as when I try to run scans in administrator mode it says avscan.exe not found. Also when it detects any virus Avira is not able to remove the virus, instead it keeps telling virus found and pops up with the window to remove