I have experienced this on two out of four laptops I owned sofar. One of them, an old PIII Compaq Armada700 had three pin cable but still pinched every once in a while. The other, Toshiba M35X, now dead, had two pins. The two that I still use that are safe are the IBM Thinkpad (a Cel. 366) and my new HP530, both using three pin cables. The Armada did not have the aluminum finish, but it still "sparked" while the HP has aluminum finish but does not spark. It is an interesting phenomenon, but I think it is not always related to the finish, nor to the 3pin issue, as my experience taught me sofar. Hope someone will figure this ou.