Windows 7: Error 651 and other issues

I'm posting this on behalf of my mate (who'll be joining up & in shortly).
He's running 64 bit Ultimate build 7100 over a PPPoE connection, and he's getting an error 651 while trying to connect via LAN 1. The motherboard has dual gigabit LAN. XBOX 360 is connected to LAN2 and is connecting ok through media extender.
He was up until recently connecting his PC via wireless adaptor which worked fine, but since installing a new LAN cable he's been getting this error.
LAN is identified as a public network, and he is unable to change it to home. When enabled, wireless is detected as home, and can be changed to public.
Any ideas on what could be the problem here?

This is only a suggestion as I am no technical expert but recently had the same problem with a failure to connect to the internet (via broadband) and "Error 651"

The way I fixed it was to re-enter the username and password for the account.

There are a few results in google on Error 651, not sure if you (Opheous) have read them?

Thanks for the responses guys.
I found a page through Google with a list of about 15 approaches to the problem, each very different. I've forwarded it on to my mate, but was kinda hoping for a more definite approach/resolution

This TechNet post might help with the unable to change network location problem.
Cannot change active network from public to home in Windows 7

This one might help also.
http://pocketpccentral.net/blog/2009...blem-resolved/