Have you got a wet dog in the house
But seriously, WiFi ain't what it is cracked up to be, and is heavily influenced by surrounding physical structures, and waves. Have you tried reseting the router back to factory defaults (usually a button) powering down everything, then powering up modem (wait 1 min)>>>wireless router (wait 1 min)>>>>then pc.
Have you tried a different postion for the wireless router, do you live in a terraced house where next door may be 'polluting' your house with waves.
Are there any strange lights outside, are there crop circles near your house, have you been having strange dreams recently....... these questions may seem ridiculous, and for a cheap laugh - but to be honest they are probably easier to answer than sorting out the mysteries of WiFi.