Wireless router dropping then disappeared (by 3 users)

SolutionLog onto the web-based admin tool of the router. Click on Tools at the top, then Misc. on the left menu..
set the following:

UPNP Settings = Disabled
Gaming Mode = Disabled
PPTP = Disabled
IPSec = Disabled 
On the computer where the connection is being lost.. go to your network connections, right-click on the wireless connection and view its properties. Under the authentication tab, you should see a check-box option for Enable IEEE 802.1x authentication for this network - UNCHECK IT!! 

Or

Change the Super G mode setting of the router to Super G without Turbo. By doing this, the connection will be stable.

My Westell modem was just replaced by a GT704WG. I've had wireless connections all week when working at my desk where the router is - less than 6 inches away. I just realized that since I moved the router several FEET away the wirless connection is now fine. I don't understand this, but it was a simple fix.

I don't know a solution but the router will appear in the list along with neighboring routers but it will disappear and the others will still be there so it's not an adapter problem something in the router stops sending a signal