Later behaviour changed somewhat (IPv4 addresses changed to reflect that of the modem's in more cases), to verify. The DHCP server in the modem interfered with the DHCP from the router, and took precedence in some cases. Since there were two separate connections to their modem, one for their VoIP phones that was direct, and one for the computers that passed through a firewall/router.
This was what I thought, the VLAN settings in their main switch were lost during a major day-long power outage over the weekend. Mix of DHCP and static, but all set IP information looked correct. Internal was 'fine', but external addresses were unreachable for those half. when dealing with computers and networks!' I'm going to yell at you for a quick second. I'm not convinced that it's a networking issues has the issue is only happening to a small group of laptops spread out through out the office.
