As you know, WEP is insecure, hiding the SSID only creates trouble for you and WPA is now insecure.

My advice is to setup the router again, pick a new SIMPLE SSID name (short is fine.) And then move to WPA2 AES personal security.

This will fix most address conflicts as the router and PCs will get new addresses. And the security will block those that are connecting to your network without permission and causing trouble.
Bob