Cisco IPSec Client does not support 64-bit. If the user requires 64-bit support, the upgrade path is to use the Cisco AnyConnect VPN Client instead, which does support 64-bit. However, the AnyConnect Client supports only SSL VPN connections (CSCsi26069).
For Windows Vista, there is no firewall support in the VPN Client. To resolve the Bluescreen issue on Windows XP related to the VPN client built-in firewall, upgrade to VPN Client version 5.0.5.x or higher.