My guess is that the problem is the 1 HP pump with 5 gallon tank from Harbor Freight. Is this what you have? http://www.harborfreight.com/cpi/cta...emnumber=47906
Where do you put air in the tank? Via the water line? Or into a separate air valve on the tank?
If into the tank, and it immediately bubbles into the supply tank then you have both a bladder failure (if it ever had a bladder) and a check valve failure.