I feel your pain! I have just lived through this - for us, it was that the router kept losing our IP/WEP address. Best thing to do is to call your router's helpline (our's was Belkin) and they talk you through what you have to do. Takes about 20 minutes and then youre back up and running. Good luck
Things that can disturb WiFi (in no particular order): 1/ Large metal objects (old steel ones) like Filing Cabinets, Radiators, Reinforced Steel Girders... 2/ Microwave ovens. 3/ DECT Phones. 4/ Wireless Video Senders. 5/ Neighbour's WiFi.
The latter is most likely to be the cause - why does every manufacturer or routers default to channel 1?
I suggest changing your channel to 7 or 11. You need to know your router's IP address: 192.168.X.1 is most likely, with X = 0,1,2 or 123. Then you need your Username and Password - check router manual. Finally you need to go into the WiFi or WLAN settings and look for the Channel setting.