I've just arrived at a friend's house for a holiday.
She has a working, internet accessing, network using a Vista PC.
I remove the ethernet cable from her computer and connect it to my Windows7 laptop and get the "Unidentified Network" problem.
if I re-connect the cable to the PC, internet access is resumed instantly. I've restarted both the PC and laptop and ARRIS TM402P/110 (modem? Router?) numerous times without helping the problem.
The network system seems very robust - just not accessible from my laptop as currently configured