1. Don't use the HardClip shader. Android devices shit a brick when you use it on some.
2. Clipping won't work if you're running it on GLES 1.1 / ARMv6. You need GLES 2.0 / ARMv7.
3. Clipping won't work if the panel's game object, or one of the objects leading up to it has a non-uniform scale (ie: 2, 1, 1 instead of 1, 1, 1).
4. When instantiating things, use NGUITools.AddChild, as it sets the layer properly for you.