Flex :: Extend ObjectProxy Class?

I trying to extends ObjectProxy class, the reason is because I want to have a Singleton of the ObjectProxy class, so I made something like

package utils
{
import mx.utils.ObjectProxy;[code]........

when I create my object uniform which is a simple object, I pass it to my UniformObjectProxy.getInstance() static method to get the instance of my objectProxy, ok so far so good.my problem is when I try to bind a property of my objectProxy instance like

_opc = UniformObjectProxy.getInstance(_uniform);
cw:ChangeWatcher = BindingUtils.bindSetter(dispatchColorChange, _opc, data.id);

the dispatchColorChange handler function is called only once an never again, I had check ChangeWatcher.isWatching() and return false meaning my objectProxy is not binding properly, if I create an objectProxy like

_opc = new ObjectProxy(_uniform);
cw:ChangeWatcher = BindingUtils.bindSetter(dispatchColorChange, _opc, data.id);

the binds works just fine, so my thinking is the problem is when I extends the objectProxy class, how is the proper way to do this