[Help me]Don't show NGUI button in menu Bar

[jameseshell]

Hi,

I using NGUI 3.7.1 and unity 4.0. Plugin NGUI not work. Error photo below:
Assets/Plugins/NGUI/Interaction/UIButton.cs(50,28): error CS0234: The type or namespace name `Sprite' does not exist in the namespace `UnityEngine'. Are you missing an assembly reference?
Please, help me.

[ArenMook]

NGUI 3.7 doesn't support Unity 4.0. It requires Unity 4.3 or higher.