Can Linux report IP conflicts?
IP Conflict detection is standardised in RFC 5227. One Linux tool that implements it is IPwatchd, which has a GNOME notification component (ipwatchd-gnotify).
you can use arpwatch to find out about ip conflicts on ethernet segment you are connected to. it will alert about unseen ip-mac combinations or whenever such association change.
I don't know the exact mechanisism of how it does it, but I've seen warnings in CentOS when bringing up a network device along the lines of "Failed to bring up eth0, a device on the network already has this IP".