A few weeks ago I tried to take my Trek road bike for my first ride since last fall. It has been sitting in my (uninsulated) garage over throughout the winter and when I tried to inflate my tires the pressure gauge on my pump showed that they wouldn't inflate. Does this sound like a problem with the pump or the innertube?
Does air leak out when you depress the valve? If so, air can get in, too, and it's your pump, or at least how you're using the pump. My old bike pump would act up like this when I pushed it onto the valve stem too far (presta valves). Could be the case for you, too.