This problem is a know bug with releases of the Cisco Systems VPN Client prior to 5.0.03. Please download the latest release. 

If the problem persists, manually enabling the Virtual Adapter can resolved problem:

• Windows XP: Select Start > Control Panel > Network Connections *. Identify the Cisco Systems VPN Adapter, this is typically Local Area Connection x (where x is a number) and is disabled (grayed out). If you are unsure, right-click and select Properties. The Connect using: field should be Cisco Systems VPN Adapter. Once identified, right-click on the Cisco Systems VPN Adapter and select Enable. Open the Cisco Systems VPN client and connect to RoamNet. 

* If this icon is not visible, select Classic View from the left hand pane.

• Windows Vista: Select Start > Control Panel > Network and Sharing Centre (icon). Select Manage network connections from the Task pane. Identify the Cisco Systems VPN Adapter, this is typically Local Area Connection x (where x is a number) and is disabled (grayed out). If you are unsure, right-click and select Properties. The Connect using: field should be Cisco Systems VPN Adapter. Once identified, right-click on the Cisco Systems VPN Adapter and select Enable. Open the Cisco Systems VPN client and connect to RoamNet.