I’ve been getting increasingly weird signal loss in my house on my wifi network.  I downloaded the freeware inSSIDer to scan the freqs around my house and found about eight different wifi transmitters (including mine) all broadcasting on Channel 6.  To try and clear the signal, I dropped the router to another lower channel — suddenly, clear, stable signal.

Might not work for you, but it did for me.  Most wifi routers are running at 2.5GHz, and there’s a few channels to choose from — 1-6, and 11 are most common; most are set to Channel 6 as their default.  The 5GHz wifi routers have a whole wheelbarrow more signals, but the theory should hold there, too.