Eclipse "Invalid Project Description" when creating new project from existing source
Solution 1:
Go into your workspace, and move your project source code folder to another area outside of your workspace (like the desktop). Make sure the project is deleted in eclipse, then create a new project from source from that directory.
Another thing you could do is try creating a project of a different name (from the first project's source), so that the workspace will contain the new project as a functional project. Then, go into your workspace directory and absolutely delete the folder that contained the original project, or move it. Try loading the project from source again, this time using the second project, by naming it with the correct name. Or, you could try refactoring the second project back to the first's name.
Solution 2:
I have struggled with this issue myself for a while and I think the reason it happens is because (for Android) there are two ways to import projects into the workspace
1) File>Import>General>Existing Project into Workspace
2) File>Import>Android>Existing Code into Workspace
The errors described here are related to method 2).
For method 1) there will be no overlap problems as long as you uncheck the "Copy Projects into Workspace" box if the project is already in the workspace.
Edit: There is a third method that wasn't in my original post.
3) File >New>Other>Android>Existing Android Project into Workspace