I have thus far tried multiple network cables (just for giggles), restarting both the modem and the router, as well as changed the router's MAC address to match the working laptop's. Oddly, this has allowed the laptop to connect through the router, but every other computer continues to struggle. I am at something of a loss...DHCP is enabled, and I have tried directly connecting to the modem with other computers to no avail.
Generally I would be inclined to blame some aspect of the hardware, but given the number of working NIC's I have thrown at this situation, the only aspect I am left with to take into consideration is the modem itself. If anyone has any ideas, I am definitely open to suggestion, anything is better then nothing compared to dealing with the cable company!
Additionally, I have played with settings in the router, as wel as the working laptop, and nothing seems to have a drastic effect until another computer comes into play, which is even more disturbing...