Doubt is's a virus related issue if you have completed a fresh install recently, however it's better to be safe than sorry, this will help you remove all the baddies:
http://www.tomshardware.com/forum/248626-45-simple-free-guide-removing-malware
Now... I would say that this is a driver related issue... could even be proxy, or Dns related... you have installed a lan card driver and now it doesn't work... Uninstall that as it could cause more issues down the track. Check if you have lost the internet connection as a whole of if it's just your browser..
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>Click start
>Run
>Type cmd into the "Run" window/Press enter
>In the Cmd window type "ipconfig -all"
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Now... Under "Ethernet adapter Local area connection" see if DHCP is enabled, and check if you have a Physical address and a IPV4 address.
You haven't said if you have any other connections to any other applications.. this will identify if there is any connection at all, or if its a setting that is configured incorrectly.
Let me know how you went