I've been happily using powerline networking for years in my condo. Now my neighbors have also installed it, and now both of us are on the same powerline network.
To make things worse, they're using the same IP address range so have totally borked both networks. They're clueless as to what has happened and can't reconfig their networking gear -- they don't know how.
I'd like to fit a filter to my electrical service panel but have no idea where to get one. That'll block their RF signal and isolate the networks.
Well... yes, except they have used both 192.168.0.x and 10.0.0.x because they don't know how to configure their equipment. And my Wii can't function on anything other than those networks -- fails to connect to the Internet on any other IP address range.
In the end, I bought new Linksys PowerLine AV boxes, which max out at 200Mbps and can work around interference from regular PowerLine networks. And I enabled encryption on both.