Scott,
I fear you may still have a problem.
If I'm reading your last post correctly, you freed one end of the cylinder and then the stabilizer arm moved freely up and down. You say the cylinder was free too. Do you mean it pivoted on the other end freely? or that the rod moved freely in and out of the cylinder?
It sounds like you think the arm goes up under hydraulic pressure, and down under the force of gravity (forgive me if I misread your post). In fact, it moves both ways under the force of hydraulics. Your cylinder is "double acting" meaning that when pressure is applied by the hose at one end of the cylinder, the rod moves away from that end, and when pressure is applied at the other end of the cylinder, the rod moves away from that end. The picture you posted earlier shows the two hoses attached to opposite ends of the cylinder.
So...if the arm moves freely with one end of the cylinder detached, then you have a hydraulic problem. If you can (with a little effort) move the rod in and out of the cylinder, then you probably have a crushed or blocked hose/pipe or a problem with your control valve.
3RRL had a good suggestion earlier when he said to try running the tractor with the at least one end of the cylinder free and moving the control lever back and forth to see if the cylinder will operate in both directions. This is a safe and easy thing to try.
3RRL and AndyinIowa posted a sequence of things to try.
Also, Willl's earlier question about whether the engine RPM dropped or you heard any squealing when you tried to lower the arm is important. You should have heard the engine RPM drop and possibly heard the hydraulic pressure relief valve squealing. If you didn't hear that, then your control valve isn't applying pressure to that cylinder. It could be as simple as the linkage from the lever to the valve came apart, but I think you'd have felt that in the way the lever worked.
Or maybe I misunderstood your last post and all's well now. For your sake, I do hope that's the case.