What does it mean if a guy won't look at you while talking?

It could mean any number of things. Sometimes they ignore you because they are upset and this is the way they handle it. Other times it is a form of control and they are punishing you for not doing or acting the way they want. Then, again they could be thinking of something. Men and women have different means of communication. When a woman asks a man to do something she will ask in a way that allows him to consider doing it or not. Men think they need to solve all problems and often will ignore a woman until he thinks he can solve a problem.