Finally!! Someone writes in with an easy problem (I hope). Your problem is with your pressure tank. It is waterlogged, which means there is no air in the tank. That results in a situation where there is nothing for the water to "press" against. If you have a bladder tank, then there will be an air valve at the top. If so, then you will probably note that water will come out if you press it. The fix is twofold:
1. Drain your tank (turn system off...open low level faucet until no more water comes out). Pressurize the tank with an air compressor to 30# or so. Turn the system back on. This will get you by for a month or two.
2. Replace the tank.
http://www.inspect-ny.com/water/Bad-Water-Tank.htm
The site above has a good description of this problem.