Computer connected to internet wirelessly but webpages won't load

Hi all, This problem is happening on a Windows Vista laptop that was recently upgraded to Windows 7. Installation went without a hitch. However, every so often, browsers won't load pages. Windows 7 says that the computer has an internet connection but for some reason web pages will not load. The problem goes away after a restart. We've tried flush dns, the winsock fix, and the problem...