Android Launching Error Unable to restore source lookup path - unknown type source container type sp

So... I have an Android project in Eclipse, which I haven't touched for a while, and now after a new installation of Eclipse, and other plugin setup, I got the following error while launching the project:
(which used to work 100% of times)

Unable to restore source lookup path - unknown type source container type specified: org.eclipse.cdt.debug.core.containerType.project

This was really frustrating, since I need to deploy a new version for that application, so I've Googled the issue, and found NOTHING...
(I would only expect that much since the scenario to achieve this is quite complicated)

I've tried the standard Eclipse issue solving technics:

• Close and open the project.

• Closing and opening Eclipse.

• Clean Build.

• Delete and import it back...

You name it, I've tried it.

Last I've noticed that also re-importing the project didn't solve it, I got the idea, that Eclipse has a reference to the project build spec, (from the .project file), referenced by the name of the project, so...
(and this is also the solution :))

1. I've renamed the project (Added '_' at the end of its name).

2. Deleted the project from the workspace (Without checking that dangerous check box).

3. Edited the .project file of the Project, and renamed it back to the original name (Removed that '_').

4. Re-imported the project into the workspace (Now with the original name).

And that is it...

Just like the lord, Eclipse works in mysterious ways... :)