Unable to connect to Network after power off

Hi
I have a strange problem.
I went away for the weekend so disconnected the power to all my appliances, including pc and router, which I have done many times previously.
On my return, I reconnected the power and booted up as usual, but the pc is unable to connect to the net. It just comes up with "Unidentified Network - no internet access".
I have removed the cable and plugged it into my netbook and it connects fine, plus I have another pc connected which is also working ok on the net. And a couple of phones using the wireless network ok too.
I've also swapped cables and ports on the router, but nothing helps.
On the pc I have a flashing orange light at the network port.

The system is Windows 7 Ultimate.
The network adapter is onboard - Nvidia nForce 10/100 Mbps on an Asus motherboard.

I have apparently been able to ping an address ok, but to be honest Im not 100% certain.

Any help would be appreciated!

 

I have checked the following services:
DNS Client
Function Discovery Provider Host
Function Discovery Resource Publication
Peer Networking Grouping
HomeGroup Provider
HomeGroup Listener
SSDP Discovery
UPnP Device Host

And they are all running apart from "Peer Networking Grouping" which is not started, and I am unable to start - it gives the following error:
Windows could not start the Peer Networking Grouping service on Local Computer.
Error 1068: The dependency service or group failed to start.

 

Update - managed to start that service.

Still no connection to my home network though?