After updating Unity to 5.6.0f3 the Bloom and Blur PostEffects throw this error:
NullReferenceException: Object reference not set to an instance of an object
UnityStandardAssets.ImageEffects.Bloom.OnRenderImage (UnityEngine.RenderTexture source, UnityEngine.RenderTexture destination) (at Assets/Standard Assets/Effects/ImageEffects/Scripts/Bloom.cs:121)
The method is OnRenderImage and its trying to access a property of the RenderTexture source (the first argument), but source is null. And the screen is black, obviously.
All post-effects receive a null as the source.