With my wife's laptop which she carries to and from work we have to change setting to use IE. What we do is launch IE. Click Tools-->Options and select the Connections tab choose Lan Settings at the bottom and unselect the Use Proxy Server box. When she is at work she has to reverse the settings. Hope this helps.
I had that issue with a new laptop with Windows 7 64bit. Turns out the Comcast-supplied netgear router wouldn't workwith WPA thanks to Comcast's custom router firmware. Changed it to WEP and all is fine.