That's exactly what I did and it WORKED.
To clarify, those of you who have Chromecast working properly on other devices but cannot connect through a WIRED/ETHERNET pc, you should look in your router settings for anything relating to IGMP and DISABLE it.
After disabling, I rebooted my router. Once Chromecast reconnected my Chrome browser saw the Chromecast device and could cast perfectly.
I wouldn't disable ANYTHING IGMP, but definitely the Proxy looks good to disable.