Actually Cisco does support Vista 64 bit and Mac OSX. It will probably depend upon your model but I'd look for an IOS update.
Found a little disclaimer on their VPN software.
•64-bit Windows operating systems. For x-64 support, customers should explore with their Cisco sales representative the use of the next-generation Cisco AnyConnect VPN Client.
http://www.cisco.com/en/US/docs/secu...html#wp1024664
The Cisco AnyConnect VPN Client supports all Cisco Adaptive Security Appliance models. It does not support PIX devices. See the Adaptive Security Appliance VPN Compatibility Reference:
http://www.cisco.com/en/US/docs/secu...atibility.html for a complete list of compatibility requirements.
The key appears to be having an ASA device if you want Vista 64 bit support.