I have a similar problem with my new laptop. In my case, I believe that it may be because I might have accidentally disabled DHCP or DNS on its wireless adapter while adding a wireless router to my local area network.
I can see all my PCs from any other in my LAN, and connect to the internet with all of them, including my laptop. But after I turn off my wireless router, I can no longer use my laptop to get to the internet through any free wi-fi hotspots the way I did even a few minutes earlier.
I am, of course, trying to resolve this problem. Stay tuned and I'll keep you informed.
I found excellent advice at: http://www.cabnr.unr.edu/IT/Wifi.aspx It turned out that I should not have specified a particular gateway in the settings of my wireless network card as I have enabled it for getting DHCP automatically.