Type or namespace could not be found - monodevelop

All of the sudden, i have 78 errors of this kind in monodevelop. In unity editor, there is no errors and also game playes ok.

All of the scripts in which the error occures are the editor scipts that are trying to access game objects.

Also, i recently installed unity 4.3. Maybe some settings got mixed or something (but i am not 100% sure this has anything to do with new instalation). Project is running in 4.2 and monodevelop 2.8.2.

Does anyone have any idea what went wrong?

When using C# you have to start it with:

using UnityEngine;
using System.Collections;

public class (insert script name without brakets) : MonoBehaviour { 

I had the same problem with namespace and this solved that. Not to sure about type. Just remember to put a linking bracket at the end of the script to link to the one after MonoBehaviour.

I checked all registries wich contained word unity and found nothing either. At the end i uninstalled unity 4.3 and everything works fine now.

Did you ever had problems if multiple versions are installed on PC?

Yesterday I had no errors, today when I loaded my project I have 107 of these errors, all for various classes. Again, everything was 100% no errors yesterday before going home.
I have no idea what when wrong, but none of these solutions will fix it (I’m already doing everything right)
MonoDevelop is just a nightmare in terms of stability for me.