Wireless keyboards on each system cross-talking to the other is the most
likely explanation I can think of.
I agree. I thought of Remote Desktop or similar, even 'spy' software that
allows remote viewing of desktops, but that would copy everything, not just
keypresses. Then again that's quite a distance for a wireless keyboard's
signal to cover. And he didn't mention having wireless keyboards -- which
would be an unusual if they are desktops.
To the OP:
If they are Wireless Keyboards, try changing the channel on ONE of the
keyboards.
If you don't have wireless keyboards...
I'm assuming they are on the same network, behind a hub or router. If they
are, do you use DHCP or assign IPs. If you do, chekc the IP settings that
they are correctly configured and different (though Windows will usually
tell you if two computers have the same IP).
If they are not, and one of them gives the other access via ICS, check the
settings of ICS, the Windows Firewall settings on each or anything unusual.
Look for any unusual programs that are running in the background.
What happens if you unplug one of them from the network?
Does it happen if you run one or both in Safe Mode with Networking?
Have you done a Virus check and is your AV software up-to-date? -- do the
check with the computers offline and disconnected from the network.
Have you run a spyware check on each?
If they are brand name systems, did they come with some sort of "tech desk
helper" app that loads in the background and allows a tech to roubleshoot
the system? If they did, it's possible that one of them is acting as a host,
the other as a remote.
If it jsut started happening, has anyone loaded any software recently that
may have started the problem?
HTH