Hello GreginHighland... and welcome,
Well, for any wireless network printer to work correctly, the wireless network printer (wnp) software typically must always be initially run on the computer device that wants to use it. This is especially true if you are changing the actual wireless connection device as is your particular case. For any wireless device that cannot run the wnp software, then it is always necessary for you to provide that device with the wnp ip address that is being used. This typically can be determined by logging into the wnp network interface and seeing what IP address is has pulled from the DPC3939B device.
Lastly, it is always a great idea to use a static IP address for any such wnp device in order to insure that it can always be accessed via the same IP. You can purchase a staticIP from Comcast for your wnp or you can modify your LAN DHCP address range to start with a higher IP address. The latter infers that you would log into the DPC3939B by connecting any computer via an Enet cable to any of the LanPorts 1-4, bring up a Browser, typw in address field 10.1.10.1, username=cusadmin, password=highspeed. Click on LAN, then edit, and change 10.1.10.2 to 10.1.10.5. While you are in here make sure you click check mark on manually assign DNS, then type in primary=184.108.40.206 and secondary=220.127.116.11. Also, make sure you Leasetime is set to FOREVER. After you make these changes, then you can program your wnp to use IP 10.1.10.2 to 10.1.10.4. Any device that you cannot run your wnp software on you will connect that device to your 10.1.10.2 to 10.1.10.4 IP addressed wnp.
Hope this helps you out.
I have recently encountered the SAME issue that the GreginHighland also has.
Prior to installation of COMCAST BUSINESS internet service or more specifically the DPC3939B Internet rounter, my iMac computer was able to "see" my Printer that is using a Wireless Parallel Port networked device that broadcasts it's sevices. my iMac was able to see the printer using the "Bonjour" services to locate these on the network with my old DSL router.
Now, with the DPC3939B router from CISCO, it appears that Bonjour services are not supported. which I find to be very very frustrating as this GREATLY interrupts my business.
BTW, PC computers on the network do not have this issue. Only Macs because i think the CISCO product is not compatible with Bonjour. Can you get a CISCO tech to comment on this?