Help Desire Z vibrate problem


At 4.30 this morning, my Desire Z suddenly started vibrating and will not stop unless I pull the battery. As soon as I put the battery back in, it starts again - it doesn't matter whether the phone is powered on or not. I even try a factory reset and that didn't fix it either - in fact, it vibrated all the way through the reset process.

I'm assuming it's a hardware defect, but I'm open to suggestions....