Ok, I'll assume that you reinstalled the software.
The only possibility is that something is blocking the connection, most likely an A/V software which may be installed on the system or was removed at one time.
Have you tried to start up in safe mode with Networking to see if the problem persists?
This Unidentified Network problem is fairly common but there are many solutions. The link below mentions one type of fix where you type the default gateway into the IPv4 properties.
There are many other solutions in the comment section below the main article. http://pocketpccentral.net/blog/2009...blem-resolved/