In preloader when you push load/install you see the boot.dol file yes. And you press load and get a black screen, or do you get a black screen when you click load/install. If you are getting a black screen when loading the dol, try to install it, then launch the installed file from the main preloader menu.
Also I am assuming you are still on 3.4u
Verify that preloader displays
System Menu v385