Unexpected error in JDeveloper 11g

I keep getting the following errors when trying to open Fusion Order Demo Applications

SEVERE: Exception while updating observer[0]: oracle.bm.commonIde.ProjectObserver@1760aec
java.lang.NullPointerException
at oracle.ide.Ide.getDefaultProject(Ide.java:487)
at oracle.bm.commonIde.ProjectObserver.update(ProjectObserver.java:57)
at oracle.ide.model.IdeSubject.notifyObservers(IdeSubject.java:98)
at oracle.ide.model.Node.notifyObservers(Node.java:786)
at oracle.ide.model.UpdateMessage.firePropertiesChanged(UpdateMessage.java:640)
at oracle.ide.model.ProjectContent$L.projectPropertiesChanged(ProjectContent.java:694)
at oracle.ide.model.Project$StorageListener.structureValuesChanged(Project.java:1097)
at oracle.javatools.data.Structure.fireStructureChangeEvent(Structure.java:455)
at oracle.javatools.data.Structure.firePlaceholderValueAdded(Structure.java:388)
at oracle.javatools.data.Structure.firePlaceholderValueAdded(Structure.java:394)
at oracle.javatools.data.Structure.firePlaceholderValueAdded(Structure.java:394)
at oracle.javatools.data.HashStructure$Impl$3.run(HashStructure.java:1970)
at oracle.javatools.data.HashStructure$Impl.putValueInKeyStruct(HashStructure.java:2021


Thanks to google and fixed by:
I have deleted the contents of JDeveloper directory after that I am able to create or open the applications in JDev- The location of the JDeveloper can be identified by referring help->about->properties->ide.user.dir)
Here are the steps:
cd /home/oracle/.jdeveloper/system11.1.1.3.37.56.60
rm -rf *

Then reopen the JDeveloper,everything works.

This error is caused by at the one point - JDeveloper crashed when I tried to run StoreFrontUI.

Mistakes I made prior: Fusion Order Demo Applications has different version for different version of JDeveloper. I downloaded Demo for JDeveloper R2 and my JDeveloper is R1.