We've purchased 100's of R930 & R30 laptops from Toshiba both have which have suffered with this problem. The R30's have brackets that stabilize the optical drive, due to the movement of laptops and vibrations of the optical drive the screws come loose on these leaving the brackets and screws floating around inside the chasis, this then results in the motherboards shorting and dying. We're trying to get our warranty company and Toshiba to acknowledge this issue, although have had very little joy at all at the moment...
It's reassuring to hear that we're not the only ones having this issue.