She also posted this in the pub. Setting up WEP encryption has nothing to do with the conflicting IPs. More than likely it is because of the rebooting of the router.the ip conflict is two pcs are using the same ip.. most likely one is hardcoded (configured on the box to not be dynamic) and the other is dynamic and pulling the same ip..
my best suggestion is have the computer wizz stop messing around and hire someone who can fix what he messed up..