Error "Invalid project description."

If you guys ever run Eclipse or Flex Builder and got the "Invalid project description" message, it usually means you guys are trying to import an existing project into a workspace; moreover, you are trying to import an existing project into the SAME directory path as the workspace.

So if you are in workspace with this path:  
C:\Projects\Project A\
and you tried to load an existing project that is located in this directory:
C:\Projects\Project A\.
This will not work!!! 

Solution:
1. Open a workspace at C:\Projects\ 
2. Import the existing project from C:\Projects\Project A\