[Laminar]

I have a Mac Mini (2.0C2D, Lion, iTunes 10.4.1), an iPad 2, and an TV. The Mini is connected to my cable modem/wireless router (Cisco DPC3825) via ethernet, the TV and iPad use wireless. I'd like to use Home Sharing, but the router itself blocks the wireless devices from talking to the wired devices. For example - with wi-fi on the Mini turned off and everything connected and enabled, I cannot see my Mini from the TV. If I plug the TV directly into the router via ethernet, the Mini's share shows up. If I leave the TV on wi-fi and enable wi-fi on the Mini, it will connect to my wireless network and I can get to the Mini from the TV.

I've disabled the router's internal firewall but that still hasn't fixed it. Anything else I can try?

[Cold Warrior]

Sounds like a subnet problem. Look for a setting in the router that may talk about guest networks, separating wifi from Ethernet, or possibly Ethernet in one ip range (10., 192.168., 172.16/32.) and wifi in another. This would create subnets and wall off the iTunes sharing traffic and discovery features, which run only within that network.

If you want, post the ip and netmask of all machines.

[Laminar]

All subnets are 255.255.255.0. I couldn't find anything about guest networks and anything resembling security within the router has been disabled (minus WPA).

[Athens]

your in WPS mode, which separates your networks. Look around for options around WPS or Wireless Protection Mode. To Disable WPS on your Router, Login to the Router setup page and click on the Wireless tab, under Basic Wireless settings you will get 2 options "Manual" and "Wi-Fi Protected Setup" so you need to select "Manual" and click on Save Settings... This will Disable the WPS on the Router.