Problems with the Mbox

[newmodel15]

I am having major problems with my Mbox. My system is an Emachine with XP, 40 Gb hard drive, 608 Mb of Ram, Athlon processor, and a soundblaster live 5.1 soundcard. Ok now my problem, first I was hearing this wierd buzzing/humming noise coming from the Mbox through my headphones, even when I was not playing anything back, and when I did play something back the buzzing got even louder. Sometimes the Mbox would turn itself off whenever I would hit Ctrl + = on my keyboard. So I thought the Mbox wasnt getting enough power, and I got a powered USB hub to plug it into and now the buzzing only occurs during the playback, but when I start up Protools and open/start a session the Mbox still turns itself off. I tried it on my dads Medion computer and it worked perfectly without the powered USB hub. Hopefully someone here can help me out.

Thanks