Unresponsive Trackpad and Keyboard

Hey! I'm having a problem with keyboard and trackpad on my macbook pro. It seems to be working fine, but then out of the blue both the keyboard and the trackpad stop responding completely. However after restarting my mac (sometimes more than once, and doing so by forcefully turning it off by pressing the on/off button for several seconds since I can't shut it down normally) they both start workking normally, until sometime later they both stop responding again. Right now I'm using both an external keyboard and mouse, and there seems to be no problem with those.

Does anyone know what might be going on? Could it be a driver of software glitch, o is it a hardware issue?

I've read a couple of threads on similar prooblems, but everyone seems to have a problem either with the trackpad, or with the keyboard, but not with both, and just for a couple of minutes. When it happens to me, they both stay unresponsive until I reboot. Thanks in advance for any comments!!!

Oh, and, also, when the trackpad freezes, its tab under "Mouse and Keyboard" in system preferences disappears...