middle manager's frastration

I work in a large bank corporation. The group is the most political and inefficieny place I ever been. I am AVP and we have another 3 VP in the group. One of VP has been there for more than 10 years and really powerful there. I did something that she told me to do. When my direct boss came back the next day, he was really mad about me. Here is the email he sent to me " what are you doing? Why you listen to her?!!!". My predecessor got into trouble by ingoring that woman VP because she controlled everything in the group.

My boss is new and he doesn't has that much power yet even they are the same level.What I am going to do? I have 9 people report to me so I have to keep the work process moving on when my boss is not there. This was what happened when I asked another VP to make decision. Everyone higher than me is my boss and I have to please everyone.I spent so much time to deal with politics and all kinds of craps during the day and I have to stay later to get the work done. Either way is wrong.It is just so frastrating to make me even thinking about leaving.