well if you now have the brightness "simple" in mce and you have run the uninstall script then it should be normal, else go and manual delete the custom_brightness in init.d and event.d then it is out, if that does not help something else is causing you screen problem, the 2x custom_brightness scripts are all that is controlling this. But even if they are not deleted your N900 will normally still blank screen as normal Did you run the uninstall?