Compatibility between Cisco DPC3008 cable modem and Gigafast WF719-CAPR Wireless-G 4-port Broadband Router

Question

After my connection with Comcast started going down once every hour or two, I went along with the tech's suggestion of getting a DOCSIS 3.0 compatible modem (previously, they kept saying that it was only needed for plans that supported higher speeds than what I was subscribed to), picked up a Cisco DPC3008 cable modem. The modem works fine, but I can't get an internet connection when going through the aforementioned Gigafast WF719-CAPR Wireless router. I previously had no trouble with my prior Surfboard, so I'm a bit leery of Comcast's suggestion that the problem is all on my end, particularly since that transitioned directly to them trying to get me to buy all of my equipment through them. I cannot make a connection with the wired or wireless connection going through the router, but I have no issue with making a wired connection directly between my computer and the modem.

Is there a known incompatibility between these two products? Is there something about the output of a DOCSIS 3.0 modem that might make it incompatible with older routers? It does look like I'm not the only one having this issue.

Comcast's position is that they don't own the router, so they can't offer any advice. Cisco says that it's Comcast's router, so they don't support it, but suggested that it might be because the router is Wireless G, older technology (which seems pretty unlikely to me), and suggests that I buy an upgrade from them. Gigafast's website does not have the product listed and does not seem to have a support page.

I'm willing to make an outlay on an improved router, but I'm a bit leery of the possibility that that one won't work and both Comcast and Cisco will throw their arms up and say it's the other person's product.

I've since talked with my brother, who's more savvy about such things, and based on the IP addresses involved (24.3.114.173 through just the modem and 192.168.1.1 through the router), he thinks that the modem is in bridge mode and is trying to assign the IP address, but the router is trying to do the same thing. So he advised me to try to modify the modem settings to operate as a proper DHCP server. No luck on figuring that out so far, but he offered to come by Tuesday and see if he could fix it for me. I will let you know if that search bears any fruit.