Turn off computer. Disconnect router, and modem from power source for 30 seconds.
Power them back on.
Restart computer.
If that doesn't work, bypass router, and connect computer straight to the modem.
If that doesn't work...
Go Start>Run, type in:
cmdClick OK.
In
Command Prompt window, type in following commands, and hit
Enter after each one:
ipconfig /flushdns
ipconfig /registerdns
ipconfig /release
ipconfig /renewRestart computer.
If that doesn't work...
Go Start>Run, type in:
cmdClick OK.
At
Command Prompt, type in:
netsh int ip reset reset.logHit Enter.
Type in:
netsh winsock reset catalogHit Enter.
Restart computer.
If that doesn't work...
Download, install, and run
LSP-Fix:
http://www.cexx.org/lspfix.htmRestart computer, and see, if it helped.
If not...
Download, install, and run
WinSockFix:
http://www.softpedia.com/get/Tweak/Network-Tweak/WinSockFix.shtmlRestart computer, and check again.