I have the same laptop, Toshiba A75. I have put on it a lot of hours, and learned a lot from it. The locking that you are experiencing is not overheating, or etc, it is the poor design of the outer shell storing static charge that does not discharge at the DC port. What I did to best stop the locking was to take a piece of tape (3 inches) and tape it to the speaker and the base. What that allows is, the speakers are directly connected to the mouse pad, meaning that now the static charge will go to proper route for discharging at the DC port.