Couldn't load a xcode project because it is already opened from another project or workspace

Question

I have a project that has one target dependency. The target dependency is dependent on a framework called Three20.

The dependency tree looks like this.

Answer 1

Quitting Xcode alone didn't work for me. What I did was:

1. File->Close Workspace/Project on every open workspace.
2. Xcode->Quit
3. Open Xcode again and open troublesome workspace