This is really strange. I have an ASUS X53E laptop with Windows 7 Home Premium 64 bit. I use it with an USB Dell keyboard and USB mouse. One day, without warning (I always wanted to use that phrase), the laptop started to send a lowercase letter Q to any command line window open.
I thought it was a problem with the USB mouse and changed it. But the problem continue. Every time I left the laptop alone for a couple of minutes, when I return using the keyboard of mouse it start sending a 'q'.
The problem is occurring even when I have disconnected both USB mouse and keyboard.