Wanted to post this as a separate thread. I pulled my hair out for a couple days trying to figure out why after a year of streaming from my wired pc to my Onkyo rc370 it all of a sudden stopped working when Verizon updated my router even though everything showed on the network on the router setting page but not my wired pc network map. (my wireless laptop did show as it was on the same homegroup). Seems to be problem for quite a few and the fix is simple but can be hard to find.
Disablig IGMP proxy in the router setting allows wired and wireless to see each other.
I found my answer in the verizon forum also and Swizzard posted the fix a while ago:
DENON 3312 AIRPLAY ISSUE RESOLVED
My provider is Verizon and I use the standard Actiontec Router given by them. I had posted up issues with this router how the 2 network devices in the router (Ethernet and WiFI) wouldn't see multicast packets across each, even on the same subnet. By disabling IGMP Proxy, it does now allow it, and continues to operate as intended: can access internet and WAN, and also use airplay...
For additional context, see: http://forums.verizon.com/t5/FiOS-Internet/Itunes-Sharing-not-working-over-wireless/m-p/197152/highlight/true#M13476
Hope this helps others as I didn't find any specific answers before other than: buy another router...