Hello,
I'm using Unity 5.5.0f3 with NGUI 3.11.0c.
When creating a new atlas, Unity freezes, my memory maxes out (16gb) after a minute or so and Unity eventually closes itself (if I don't force it to close) without any errors. The atlas prefab is created but the texture is not.
At first I thought it was the project since it's large, but it also happens in a new project.
Any help would be appreciated, let me know if you need more info.