strange problem with LAN

[Gerhard Magnus]

I have assigned IP addresses to the boxes on my home network,
192.168.1.11 thru 192.168.1.14.  This arrangement has worked without
problems until today.

When I booted up the machine at 192.168.1.13, instead of the usual
report of eth0 being activated I saw an error message: "Some other host
already uses 192.168.1.13".  I was unable to ping 192.168.1.13 from
another machine.  Box 192.168.1.13 remained unconnected to the LAN until
I manually activated eth0 using system-config-network.  Then everything
worked normally.

I rebooted another of the boxes 192.168.1.11 and got a similar message:
"Some other host already uses 192.168.1.11".  Again, activating eth0
solved the problem.

What's happening?  Is there an easy solution?  If not, what can I do to
troubleshoot this further?

Thanks for the help!
Jerry