Unity3D START!!!!!!!!!!!!!!!!! - My solution for this exception: BCE0021: Namespace 'System.Collections' not found, maybe you forgot to add an assembly reference?

Yesterday night I have built a simple Unity3D project. It can be compiled thoroughly and it works.

However no wonder why when I tried to open the project and run the project today. I got this weird error:

BCE0021: Namespace 'System.Collections' not found, maybe you forgot to add an assembly reference?

This error happened when I wanted to open a JavaScript file in Unity3d and then the MonoDevelop crashed......

I have deal with this error for few minutes and discovered that it is just because you have a file named "System"!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! ...... That's all...

My solution is that I just changed that file into another name instead of using the word “System”. After that my MonoDevelop works fine and I can continue to build my simple Unity3D game ( Ｔ ▽ Ｔ )ノ

So it is probably that the word "System" is definitely not good to be used as a file name. Need to be quite aware of that.

Cheers~~~（≧∇≦）

Remarks:

The version of Unity3D I used is Unity4. However the MonoDevelop always freezes thus I am going to switch to other editor soon.

In together with Unity3D probably I will use Blender to build some 3D images and products so that I can use them in Unity3D and build apps. The reason for using Blender is because it is free J Maya and other products are quite expensive. Will try to stick to Blender and see.

Moreover, just one more point, the Unity3D has an app on Android which allows us to test the project immediately which is very convenient.