My approach would be to simply uninstall Avira and reinstall it/update it.
AV programs, like any other program, sometimes develop damaged files. In which case the program needs to be repaired...reinstalling (after uninstalling) is the only repair option for most programs.
It seems that you have been using msconfig to manage startup items...it was not created for that purpose and is a poor tool for such, even though many persons suggest using it to manage startups.http://support.microsoft.com/kb/310560
There are any number of startup managers that perform that task reasonably well...and better than msconfig.