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.
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.