Apparently the FIOS Router (Westell 9100 in my case) doesn't like the IPv6 that Homegroup uses. I lost DHCP service on all three computers that have Win7 installed. I could manually set the IPv4 addresses in the Network Connector options on my computer and every thing worked fine. If I tried to use DHCP for IPv4 I wound up with a private network address (169.xxx.xxx.xxx).
DHCP for IPv4 worked fine adfter I disable IPv6 and the associated topology services. I also removed the HomeGroup option from our network setup.
If you want to use home group be prepared to manually set the IPv4 addresses in your network devices.
Are these Windows 7 PCs that you installed 7 onto yourself, or ones that came with it? I have an HP laptop that came with Windows 7 already installed, no issues at all about IPv6 that I know of. IPv6 is still activated, works just fine on my FiOS Actiontec router, but maybe the Westell is just enough different to be sensitive to that.