Unfortunately, my parents 23 year marriage was ruined by my father's mother, and his failure to deal with her. She was very underhanded, but a major troublemaker. She never wanted the two families to have peace, and would hold grudges.
As for your situation, I would sit down, and have a very serious talk with your husband. Explain to him that as his wife, you deserve to be treated with respect. Since it is his mother, he really has a responsibility to prevail upon her to change her ways. Even if she doesn't like you, for whatever reason, for her son's sake, she needs to learn how to work with you, so that her son's marriage and life arent negatively affected. In laws, family, and marriage are about working at things, compromising, and seeing the other party's side. This is where my father and his family failed, and why my parents marriage failed. They could never see anyone else's point of view, pain, or feelings. In your case, I think he really needs to talk to his mom.
Good Luck. I hope all works out for you.
Mitch