hi,guys. i am confuse that G4 Cube speakers would need so much power? i plug it to usb port, sometimes it works, but sometimes didn't work, and when it didn't wokr it would cause usb no power to output, mouse and keyboard wouldn't work. my G4 Cube, 1.8g cpu, 1.5g ram, 120g hd. without the speakers, mouse and keyboard would work again. should i replace my logic board? or any else way to solve it ? i had tried reset pram and pmu.