The same issue also occur when you get update from Beta version of the new MT4.
But I am using the free version of Avira. I don't know about the paid version.
I have received since 01.23.2014 10 x Virus 'TR/Crypt.XPACK.Gen' is a Trojaner for Spionage
I have MT4 and this had not to do with the update. The Virus is in the Metatradermanager
and Metaquotes sent out this Trojaner with a .exe Datei. This is criminal from Metaquotes.