My issue is 99% identical. Running both PasswordMaker and Download Statusbar on Firefox 4 (and now Firefox 5), I could not access the PasswordMaker Options window via the add-ons bar, right-clicking on a password field, or the Tools menu: it was always blank except for the close button. The only way I could access the PasswordMaker Options window was via the extensions manager. Not exactly the best workflow, even for a workaround.
Like everyone else, disabling Download Statusbar temporarily fixed PasswordMaker, so now I can view the Options window using any of the available methods.