Neither

Have you done anything different with your DSi recently, such as using an action replay or downloading an app? I've had this problem before when I leave the DSi on for too long with the action replay inserted. My common fix for this is trying to boot the game as fast as possible when the DSi powers on. Is there any additional information you can provide about your problem? Can you boot other apps within the DSi? have you considered erasing all the data that is currently on it through the settings menus? Since the menu boots, trying blowing compressed air or using an air blower in the cartridge slot, this may be the source of the issue. Hopefully some of this helps!