go to the "control panel select admin tools then services" then scroll to the bottom and anything that has to do with the internet return it on to automatic or manual, do the whole page if necessary. then reboot, this may do it.
After doing almost everything I could think of, and many of them multiple times, i.e. summary. Updated drivers, uninstalled and reinstalled devices, cleaned (full) laptop using all Norton utilities. Followed Acer support instructions, big mistake, took me to blue screen and corrupted startup. Restored to earlier saved date. backed out all atheros updates. etc, etc, etc. You get the point. By the way, my environement. Cable modem, belkin wireless router, Acer aspire 5734Z, Windows 7. Every other device in the house could access wireless but this PC. Solution: Purchased Linksys E1200 N300 Wi-Fi Router. Recoverd everything that I had done to Clean the machine. Installed router CD, laptop not connected via ethernet, followed installation directions and everything worked perfectly. Easiest install I have had. Reconfigured all other devices in no time. Will monitor over time but it looks like I am back in business. Hope this helps. Aside from scrubbing the laptop and doing normal maintenance, all of the other things suggested appeared to be a waste of time. In the end it was the wireless router that was the problem. How did I come to this conclusion. Went to a McDonald's and connected to 4 different hot spots in the immediate area with no problems. Ruled out that the wireless on the laptop wasn't working.