Compiler suddenly started showing errors for seemingly no reason.

Some of my scripts have suddenly started showing compiler errors for no apparent reason.Essentially they all have a variation of this kind of thing:

using UnityEngine;
using System;
using System.Collections;
using UnityEngine.UI;

public class sampleScript : MonoBehaviour {

public Sprite m_Sprite;
public Image title_Image;
void Start (){
title_Image.sprite = m_Sprite;}

And are showing a compiler error like this:
‘Image’ does not contain a definition for ‘sprite’ and no accessible extension method ‘sprite’ accepting a first argument of type ‘Image’ could be found (are you missing a using directive or an assembly reference?)

It doesn’t make any sense to me…It was working fine an hour ago, and I haven’t done anything to these scripts in that time…

Any idea what is going on here?

Like Hellium said you have created (or imported) a type in the global namespace which is named “Image”. You should either rename your own type or place it in your own namespace to avoid name collisions.