I believe this is a real BIOS virus
I started having the same problem. I was using a USB keyboard. Bought a brand new USB keyboard, but problem persisted. Tried the new keyboard on different USB ports. Reinstalled OS from scratch on a brand new HD. Checked with several anti-viruses, anti-rootkit, anti-malware and found nothing suspect. Still my keyboard behaves erratically - it starts repeating the tab key when I press it once and only stops when I press caps lock or ESC. Sometimes starts repeating by itself. It usually starts repeating as soon as the computer is turned on, ie, even before windows is loaded. Left shift does not work. The letter A cannot be made uppercase with either left- or right- shift, only by using caps lock. Both keyboards have presented the same problem.
I am stil researching what to do. Restoring BIOS default values did not work. It seems that removing the battery from the BIOS and replugging it, according to some technicians, may work. I have not tried that yet. A more dramatic solution would be to update the bios directly from the manufacturer's site.
I will keep you guys posted. Only wrote so far before I have a solution because I didnt want the topic to be closed on a general conclusion that it was just a faulty keyboard. It seems that this is a new situation, many people are experiencing this erratic keyboard behaviour, with subtle differences, and they can never find a virus on their system. It usually follows invasion by a trojan that is later removed (as in my case). I will post what I discover.
