It seems HomePlug certified powerline networking components aren't as interoperable as it would first appear. I've been using Devolo Homeplug dLAN 200 desk units for a number of years now and they have been trouble free and constantly out perform wireless networking in terms of speed. I recently bought another Devolo dLAN 200 unit to expand my network to enable streaming video to a Windows Media Extender.
I assumed it would be a case of just connecting it to the mains and using the Devolo dLAN configuration wizard to set all the units up with a new encryped password. I soon realised that this wasn't the case.
The dLAN configuration wizard didn't even detect the new unit on the mains network. After looking through the manual for a while scatching my head searching for a non-existant troubleshooting guide, I spotted a paragraph that mentioned that older Devolo products using firmware 1.x need their firmware upgraded in order to work with newer models.
Upgrading the firmware has now made all my dLAN 200 HomePlug certified devices compatible! Thank God for standards