I have this same issue on our network. Spoke with Teamviewer, and its an issue with the Avast. The only two work arounds are:
1) disable the self-defense module. This is really not a good workaround
2) use an remote desktop connection, which means a VPN connection if not on a network, again, this is not always possible, and kinda defeats the point of using teamviewer
This has only been an issue recently, so must be due to an update of the software by Avast
I cant believe they cant recreate the issue, that's not possible.
I've just logged it with Avast support, so will update on any replies.
Avast request no. is: 06703302
thanks
G