I have a Cisco ASA 5505 that connects an office of 10 phones and 10 PC's to the main office via VPN. The phones work fine but only one PC has internet and that is the Windows 7 machine. None of the Windows XP machines can ping outside of the local default gateway.
I remoted into the W7 machine and took off IPv6 and it lost internet. When I added IPv6 back, it could get on the net. I added IPv6 to a Windows XP machine but still no internet.
DNS- resolves to ISP
Please let me know if you need anything else.