installing a suspected Wii-menu.wad is something like suicide. ( "don't listen to the guy on the forum".....the story i learnt from my mother. :P )
uninstalling a sysMenu,but not replacing, puts you into black screen.
press and hold the RESET key before you power on the Wii...... any finding ?
if you have Bootmii installed as boot2, insert the SD card with bootmii folder and NAND backup files for recovery.