I think your router might be switching from G to N or back. When you have multiple wireless computers if they have different Wireless standards (like 802.11G and 802.11N) then this could happen:
If a computer is turned on that uses G, the router will switch to G to use that standard. and if another computer tries to access with N, the router will then switch back to N. when this happens, the computer using G, will lose connectivity. turning the wireless on this computer off and then back on will send a new request to the router that will then switch back to G.
I don't know if this is your case or if I got that written out correctly, but this might be what is happening....
Note: this is just a shot in the dark so if it doesn't help, disregard
Depending on what router you are using, you can try something like this to resolve: http://smallbusiness.chron.com/chang...ter-34829.html