I've been battling this one for a while as well, and what happens is when you plug in the power cord, the wireless device is disabled. If you pull up Device Manager, you can reenable the device there. I'm on a Dell Latitude E6520 with an Intel Centrino Advanced-N 6205 wifi device. This happens every time I plug in power, either on the laptop or when docking. I've gone through all power settings and driver settings for the wifi device, tried three different driver versions from Intel and Dell, to no avail. If anyone has solved this, tips would be appreciated.