Really need help with: Ambiguous reference 'constructor': UnityEngine.GUIContent.constructor(UnityEngine)

So I installed the FPS controller pack, and there is a script called proGRids that causes a problem.
Here is the whole error line, and I didn’t code this, so it was above me.

Assets/6by7/ProGrids/Scripts/Editor/ProGrids_GUI.js(108,55): BCE0004: Ambiguous reference ‘constructor’: UnityEngine.GUIContent.constructor(UnityEngine.Texture, String), UnityEngine.GUIContent.constructor(String, String)

Anyways, thanks for help in advance!

see this Welcome fpscontrol.com - BlueHost.com