Why does my laptop keyboard freeze up and go nuts?

Sometimes my laptop will temporarily freeze for about 4 seconds, and then when it unfreezes, the keyboard starts going nuts. Sometimes it will beep like crazy, sometimes it will retype and spam the last 4-5 sentences I've typed out, and then all of a sudden the keyboard just dies. I can't type using it, can't use my mouse to do a soft reboot because it's spamming random letters, so I have to end up doing a hard boot.

This often occurs when I am playing Minecraft or doing other graphic-intensive things. Any idea at all why my keyboard goes nuts like this? It's becoming quite a problem when it happens in IMs with people, sometimes it magically retypes out a recent password I've entered, etc.