UE4.10 crashes since I install UE4.11

We are using 4.10 to develop my project. It is a multiplayer game. But after I install UE4.11, when I want to run more than 1 editor windows in UE4.10, the UE4.10 always crashes. I suppose maybe I did something wrong in my BP, but after 3 days testing, I finally figure out the 4.11 is virus for 4.10!!! Please fix this , thank you very very very much!! This problem almost kill our project!!