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

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.

myProject
   -> myCustomFramework
         -> Three20

When I tried to build and run I get the following error message.

Workspace Integrity Couldn't load Three20.xcodeproj because it is already opened from another projet or workspace.

I have only one project open. Any suggestions on why I am getting this message?

Solution

Quitting the xcode completely and opening it up again worked.