Signal Problems

I was previously using a linksys wrt54g wireless router, and was having good luck for a while, then suddenly I would only have about 1 bar of signal on my airport. I recently switched to fios, and thought maybe their router would do better. My signal still comes and goes.

Where do i start, as far as locating a problem? When i do a speed test, I'm not getting anywhere near the speed that i should be getting. I have the fios 20/20 service