Ethernet problem

I have MSI K8NGM2-IL motherboard. It has in-built VITESSE VSC8201 RX/ Realtek 8201CL LAN card. From the manual of the motherboard, I got this. My Device Manager (in Windows) shows the Network adapter's driver is provided by NVidia.
The problem is after one or two successful connection, my LAN stops responding to my ADSL. Now the output of ifconfig eth0 shows that LAN works fine with static IP 192.168.1.100 (subnet: 255.255.255.0, getway: 192.168.1.1). But when I try to test my ADSL by ping 192.168.1.1 it shows that there is no such route to connect the destination.
Now I am not sure that this is due to driver problem, because it worked after fresh installation. What is the problem ?