"The default gateway is not available."

I bought a new computer and received it today, it's running Windows 7 (64-bit) everything worked fine for about 15 minutes or so until it began randomly disconnecting. When I would run the troubleshoot manager I would always get the same response: "the default gateway is not available". I'm not sure if it has to do with my installation of AVG or is there more to this issue than I thought. I did some research and it seems that other people are having the same issue as well but I'm not sure what to do about this...Any suggestions??

I don't have an Nvidia driver, I have a Realtek ethernet driver, a friend suggested that I uninstall it and reinstall it which I did and worked for the remainder of the day until later tonight, it's not as frequent as it use to be but still as irritating...Any ideas??

I have Windows 7, would this still apply??

System Manufacturer/Model Number N/A OS Windows 7 64 bit CPU AMD Phenom II X3 Triple-Core Processor 710 (2.6GHz) AM3 Motherboard MSI GF615M-P33 Socket AM3/ GeForce 6150SE/ DDR3/ A&V&GbE Memory 4GB STT DDR3-1333 2GB/128x8 CL9 Memory Graphics Card(s) nVidia GeForce 9800GT 512MB 2DVI/HDTV PCI-Express Video Card Sound Card Onboard Audio Monitor(s) Displays N/A Screen Resolution N/A Hard Drives 320GB SATA2 7200rpm 16MB Hard Drive

It disconnected me for the rest of the night last night, and when I tried to fix the problem it either shows up with "There might be a problem with the driver for the Local Area Connection adapter" with the occassional "The default gateway is not available". Sometimes the error diagnosis claims that the ethernet cable isn't plugged in when it is. By the way when this happens it automatically reconnects a minute later...Also no one else in my household is experiencing this issue. I'm assuming it may be a hardware issue considering when I uninstalled/reinstalled the Realtek ethernet driver it worked fine for a couple of hours and later on the error persisted.

I got the computer yesterday its been like this since I got it. I got d/c'd again just now with another error this time stating "A network cable is not properly plugged in or may be broken".