Things to try...
Try unplugging the main cable or dsl modem (not the wireless router)... Let it sit 5 min... Plug it back in and then try to reconnect on your wireless computer... CHECK to see if its working......... If not, then unplug the wireless router this time (leave modem alone) and let it sit 5 min and then plug it back in.......... Sometimes the modem/router just needs to be reset...
Try disabling any virus software and/or firewalls and then attempt to connect... If you do, you found your problem...
Try running adaware and virus software to make sure your computer is clean of things that could be causing a problem with your connection....
Try making sure you didn't block the internet in your firewall or virus software...
Try turning down the security level in your browser....
Try going to RUN and type CMD... That'll bring up dos (C: prompt) .... type:
netsh int ip reset resetlog.txt
That sometimes helps me if i'm having connection problems... Not sure if it'll help in this scenario though...
Hope one of those works for you... Could be a million things!