May be the signal problem, I also have an HTC phone, HTC WIFI signal antenna in the middle shell above. Depending on the phone model, mine is the position of the evo on the back shelf of the phone. There was a fall before, so the inside contact fell off a phenomenon that often causes the WIFI connection to appear unstable signal.
Later, I took apart the wifi contact and the antenna together to solve the problem, and now basically there is a signal from about 10M.