After PMing ED, he suggested that I run op_test_inputs.  It seems my right nub is definitely dead  

   However, the left nub is working perfectly according to the test page.  The blue icon moves around smoothly at a consistent speed.  The numbers show up yellow (which I believe means they're ok) so I don't know what's up with the diagonals :/  Calibration in the applications?  It's very strange because no matter what values I change in the Mupen plugin config file, nothing changes the diagonals