I have the same problems as you. I upgraded Android Studio to version 2.0, which also updated the Android SDK.
I believe that this problem is more likely related to the Android SDK problem, since I directly use the AVD Manager SDK. I can reproduce this problem.
As another data point, I also modified the virtual device to use only 768 MB of RAM, without any consequences. The task manager shows the emulator using 2 threads and 13% CPU no matter how long I left it, but the window never appears. I tried with and without HAXM. My virtual devices operate at API level 21 (x86_64) and 19 (x86).
I also reinstalled Android Studio and Android SDK without any changes. This could be a configuration issue due to upgrade 2.0 and the SDK, a broken version of the SDK, or something else.
Returning to the Android SDK 24.4.1 allows the emulator to work again , but without the functions of 25.1.1.
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