Darren Myher's Blog

After applying recent security fixes for Windows 8.1 (https://technet.microsoft.com/library/security/MS15-011) my Cisco ANYConnect client failed to load.  Error:

Cisco AnyConnect: Failed to Initialize connection subsystem.

I’m not sure what it is about the most recent security updates that made it stop working, but I found that by setting it into Windows 7 Compatibility mode the issue was resolved.

The registry hack for doing this was:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows
NT\CurrentVersion\AppCompatFlags\Layers

Add a string value with the string name set as the full path to this file:

C:\Program Files (x86)\Cisco\Cisco AnyConnect Secure Mobility Client\vpnui.exe

Then set the string value to:

$ Win7RTM

After making the registry change, right-click the AnyConnect icon, and choose Quit:

Then re-launch the AnyConnect client. and all seems to work.