Hi,
You also tried with 2 Win7 laptops .
This is not a laptop problem. You have tried 4 different machines and get the same error.
Is it possible that you could post the address of the problem site?
As Nev says - this is either an ISP problem or a problem with the site itself.
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Try pinging the site from your Win7 machine
Start .....type in .......cmd .........do not hit ENTER yet
Right click on cmd.exe that appears top left of screen > Run as Administrator
At the prompt type in ..............ping www.***********.com ( address of the site ) > ENTER ( space after ping )
You should get 4 packets sent and no losses.