Enum has "Unknown resolve error"

In my code, I have an enum that says the keyword is Unknown resolve error. The enum can’t be used, and doesn’t exist.

using UnityEngine;
using System.Collections;

public class BaseWeapon : BaseStatItem {

	public enum WeaponTypes{

	private WeaponTypes weaponType;

	public WeaponTypes WeaponType
		get{return weaponType;}
		set{weaponType = value;}

Can someone please help? I’m following this video and I have no clue what I’m doing wrong.

Unity 4.5.5f1
MonoDevelop 4.0.1

Really Sory, but after my PC crashed everything worked fine. The errors were all in Mono, I didn’t even need to go into Unity to see them. It was all because of that Unknown resolve error, which I can’t recreate. Can anyone tell me what Unknown resolve error even means?