And not a word about the router settings. For example all this does happen on insecure wifi routers and of course routers that have issues. But your post does not reveal the settings.

While we cover this in the Cnet Networking Forum STICKY posts here's the short version.

1. Router defaults.
2. Simple SSID that is broadcasting (hidden SSID can mean drops.)
3. WPA or WPA/WPA2 or WPA2. Use the settings your machines support.

That's it. Do not hide the SSID, don't use MAC filters and don't think that open or WEP helps.