There is a bug in Windows 7 that doesn’t allow the wireless networking to connect to anything once in a while. What happens is that when you wake the computer up from sleep, it doesn’t connect to the wireless network. It can show different statuses and none of them may be correct.
For instance, I may bring my laptop home from the office, and when I open it up at home, it will show that it’s connected to the office wifi for 10 or so seconds. Then it will go to a red-x and show no available connections, or maybe what was available at the office. You can get this reconnected in a few ways. 1. wait for a couple of minutes and it will probably connect. 2. reboot and it will connect. 3. disable the wifi and enable the wifi and it will probably connect (not the physical switch, but the adapter properties).
I experienced this on my Latitude E6510 maybe 30% of the time. I experienced this on this new Precision M4800 laptop maybe 90% of the time. Except that disabling the wifi and enabling it, wouldn’t fix it. I would have to sit and wait a couple of minutes, or reboot. This has been such a pain to deal with. My new computer is very fast, except for when connecting to a known network.
So I decided to load Windows 8.1. My computer came with a Windows 7 license as well as a Windows 8 license. I decided to try out Win8.1 and see how it goes.
Windows 8.1 has almost solved it. I now come across this bug maybe 5% of the time. And when I do have a problem connecting, it almost always resolves itself quickly.
All this leads me to believe that it is definitely a Windows bug since it has happened across different hardware, with different wifi adapters. Many people have posted to disable “Let my computer turn off this device” but this never did anything to fix my two computers.