Most likely cause (other than a local jammer), is that the garage door transmitter is locked up and outputting a mass spectrum of RF noise

(I've seen this in 3 blu-ray players working the other way where their WiFi cards go bad and blast wide spectrum noise knocking out any wireless communication from about 29hz past 6ghz). this is usually for about a 10-15 radius though; and is why its more likely on the garage side as their range is generally greater then wifi

(yes I know this is related to frequency band, but it is still generally more powerful than a wifi signal unless you use a high power or longer range access point).