Cursor And Keyboard Freezing, But Computer Remains Active?

just the touchpad. My problem is that sometimes, my cursor will just...jam. Like, stick in some spot on the screen. When it does that, my keyboard will also go dead, and nothing seems to revive it (holding down Ctrl+Alt+Del does nothing; nor does the Esc button). The thing is, though, activity still remains on screen. It's not like that part of it freezes up. For example, I've had it happen to me when I was on Twitter, and yet new tweets came in. And today, when I was filming myself with my webcam, it happened and I was still able to see myself moving in the webcam -- yet I couldn't do anything with the cursor or the keyboard.