First off, try checking the kegging sticky as I think you may have too little hose for the pressure. As far as the pressure dropping, I think you may need to adjust the regulator a bit better. On the regulator I've been playing with I need to go slightly past the amount and then it will settle in at the correct pressure.
Primary - Apfelwine
Secondary - Niagara white wine
Kegged - AH Special Holiday Ale, AH Cream Ale, AH Honey Wheat
Bottled - Continental Pilsner, Island Mist Mango Citrus, Island Mist Wildberry Shiraz
Up next - AH Foster's clone, Labatt's clone, Hard Apple Cider,
The Independence Street Brew House