About a week ago, my Toshiba laptop started having a very odd problem connecting to wireless. When I boot it up, or when I disable and re-enable the network adaptor, it shows that it is connected to the correct wireless network, and that it has internet connectivity. Within seconds, it loses the internet connection. Pinging either google.com (or another named location) or even an IP address fails. I can't connect using a browser, etc. A wired connection works perfectly.
Also, while booting up, it can be seen in the local workgroup by other computers (peer to peer), but as soon as the internet connection is lost, it is no longer visible to the other computers. However, the laptop still shows that it's connected to the wireless network (and shows 5 bars of signal strength, but a yellow triangle that, if you hover over, says "no internet connection"). I've tried using both the built-in wireless adaptor, and an external USB adaptor (D-Link DWA-171).
I've tried disabling the Windows firewall (there's no other firewall). Disabling and re-enabling the adaptor (or even unplugging and plugging in the USB one) brings a few seconds of internet connection (and any page which was hung during loading will load during those seconds), but then the connection is lost again. I thought maybe the D-Link connection software was causing problems, so I removed that and reinstalled just the USB driver. No dice.
I'd appreciate some help in further trouble-shooting. This is very annoying, since I can get that few seconds of internet connection, and then it goes away.