Hi,
1. Which version of Windows is installed on the computer?
2. Is the issue specific to this particular website?
3. Are you aware of any changes made to the computer, prior to the issue?
Method 1:
Boot your computer in safe mode with networking and check for the issue.
Start your computer in safe mode
http://windows.microsoft.com/en-US/windows7/Start-your-computer-in-safe-mode
**Note:**While at the advanced boot options, select Safe mode with networking.
Method 2:
a. Click on Start, click All programs, click Accessories, right click on command prompt and select Run as administrator.
b. Type in the following commands, one at a time and hit enter.
NETSH WINSOCK RESET
NETSH INT IP RESET
IPCONFIG /FLUSHDNS
c. Exit the command prompt and check for the issue.
Method 3:
Update the network adapter and check for the issue.
Update a driver for hardware that isn't working properly
http://windows.microsoft.com/en-us/windows7/Update-a-driver-for-hardware-that-isnt-working-properly
Update drivers: recommended links
http://windows.microsoft.com/en-US/windows7/Update-drivers-recommended-links
Hope this helps.