I have a recent issue with a keyboard/mouse combo. Some keystrokes and mouse down/mouse up events are ignored; in other words, if I type: "Hello World", I may find myself with "Hllo World". Sometimes everything is ok for hours; sometimes, it may completely block the keyboard for a few seconds.
First, I thought that since this is a cordless keyboard/mouse combo, there is an issue with radio signal, especially since what I observe is very close to what would happen if the receiver is too far away from the keyboard/mouse or if something in the middle is blocking the signal.
It appeared that the problem is exactly the same with an ordinary, non-cordless keyboard.
How to diagnose this issue, keeping in mind that:
The risk to have malware is pretty low and recent scans shown nothing,
The PC has Windows 8 Consumer Preview,
Windows was installed months ago, while the issue with the keyboard/mouse is recent (two weeks),
There are no special drivers for keyboard/mouse to install/reinstall,
The ordinary keyboard/mouse combo is used through USB. The other, non-cordless keyboard, uses PS/2,
The mouse motion seems unaffected (but mouse buttons are affected).