Use the debugger. Set a breakpoint on the line where you retrieve the proxy and run in debug mode. When it stops on the breakpoint, check the variables (turn on 'Flex->Show inacessable member variables on the variables view menu; the little down arrow on the right side) so you can see everything.
If its there, then do 'step into' ant step through the code a line at a time and see where the ball is dropped. From your example, I don't see the type of your local var called accessProxy. Is it defined as var accessProxy:AccessProxy?
BTW, if you're not using Flex Builder, this is why its woth buying. Trace statments are from the stone age.