If I had to pick the most popular subject people call my show about, it would be mother- and daughter-in-law relationships.  Here's why:
 
Mother-in-law's perspective 
 
The mother-in-law has been the number one woman in her son's life for the past two or three decades. She gave birth to him, raised him, loved him, kissed him, hugged him, nurtured him, and disciplined him. Then suddenly, a younger, less mature woman comes into the picture, takes over, and (typically) behaves as if there can only be one woman in his life.
 
In addition, the mother-in-law no longer has a clear idea of her role in her son's life. For the daughter-in-law, it's simple - she's his wife. But for the mother-in-law, it's not so cut and dry.  The daughter-in-law doesn't understand this because with her mother, it's almost as if nothing has changed. The daughter-in-law's mother isn't expected to do guy stuff with her son-in-law. All she has to do is be nice when he shows up, hand him a beer, turn on the game, and he's good to go. 
 
Daughter-in-law's perspective 
 
The daughter-in-law is the newcomer. She doesn't like getting advice and opinions from a more experienced and mature woman because it tugs at her insecurities as a wife and mother. Insecurity leads to defensiveness, defensiveness leads to snottiness, and snottiness results in harsh words and hurt feelings.
 
The solution
 
The mother/daughter-in-law relationship requires an intense amount of compassion, sensitivity, thoughtfulness, and gratitude on both sides, even when you want to strangle each other.  
 
Mothers-in-law need to realize that it is not a competition. You also must give your son and his wife space. Don't show up unannounced, and ask if certain things are OK beforehand.

Daughters-in-law need to make their mothers-in-law feel as at home as they make their own mothers feel. Just because a man gains a wife, doesn't mean he has to lose a mom. Don't treat your mother-in-law as a problem, and don't feel annoyed or put down if she offers help or advice.  Giving advice isn't mean or insulting. We all have something to learn, and besides, without your mother-in-law, you wouldn't have your husband. Remember: The reason he's so good to you has a lot to do with the woman who raised him.