Even by checking google, I still got trouble for a while on QObjet classe inheritence.
Here is a simple polymorphisme interface I wanted to acheive, but I got ambigous base error compilation w/ QObject by creating seriealNetwork and EthernetNetwork object.
FYI : seriealNetwork and EthernetNetwork use signals & slots
(Incoming interface -_-)
you have the "diamond inheritance problem":http://en.wikipedia.org/wiki/Diamond_problem#The_diamond_problem.
You inherit QObject multiple times, but you should do it only once.