I posted elsewhere on this but just in case it's of use for someone I thought I would start a new thread.
As per RD-83's post over here, I've had issues in the past with my Powerline device losing connection. After reading about keep-alive pings sorting it I wrote a (very) simple app that pings a specified address, at the specified interval. The app then writes to a text file when the ping fails, then again when it succeeds.
It appears to have helped me. I have it called as an app from the SSC and it starts pinging when it fires up. Any questions let me know.