Keyboard Performance: Does Not Enter All The Keys

I type about 40 words per minute, but when typing on my home computer it does not enter all the keys that I hit. It is no particular key but more like there is a micro-second stall in the computer somehow that prevent the keyboard stroke from being recognized. I notice it most while using internet explorer probably because that is what I use most, but have had it happen while using other programs. After typing a page or so, I look to the screen to find a dozen or so misspelled words due to this problem. I have Windows Vista as the operating system.