You may get a message from the Cisco VPN client stating that it failed to enable the virtual adapter within a Windows 8 environment. To resolve this you’ll have to edit the registry and no reboot is required:
1) Open the registry editor by pressing the Windows+R keys together simultaneously to open the “Run” menu, then typing “regedit” without quotation marks inside the field and press enter.
2) Navigate to: HKEY_Local_Machine > System > CurrentControlSet > Services > CVirtA
3) Select DisplayName
a. You should see an entry with a string similar to: @oem8.inf,%CVirtA_Desc%;Cisco Systems VPN Adapter
i. For x86 systems, modify the value so it only states: Cisco Systems VPN Adapter
ii. For x64 systems, modify the value so it only states: Cisco Systems VPN Adapter for 64-bit Windows
*If you are not sure if you have an x86 or x64 system, open your Control Panel, select “System”, and you’ll see an entry that states “System type:”.
Try to connect again and it should work.