I guess you will find Dot.Net Framework 4.6 installed on your core server.
When you uninstall the correspondig microsoft patches, how discribed here: Core Server Activation utility crashes the activation should work again.
You can not find .NetFramework. 4.6.1 in "Add/Remove Programs"
You can find it to "Installed Updates" in "Windows Update" tool.
.Net Framework 4.6.1 can be removed by uninstalling "Update for Microsoft Windows (KB3102467)" (Reboot required at the end).
To prevent further installation of .NetFramework 4.6.1 by Windows Update you can create a registry key: https://support.microsoft.com/en-us/kb/3133990
You can use this Microsoft tool to verify if .NetFramework 4.6.1 is installed or not: http://blogs.msdn.com/b/astebner/archive/2008/10/13/8999004.aspx
I hope that this elements help you.
it turned out to be DNS errors on my end. i had my sys-admin to edit some entries and i was back in business. i was able to update the AV and it has been making its way around the clients. i am going to go read on how to upgrade to the next service pack. but this issue is no longer an issue.