Missing project nature class for org.eclipse.jdt.core.javanature

Hi all,

I have just installed NWDS standalone. I haven't set any configuration about J2EE Engine. I have imported the webdynpro example "welcome". I get the next error when I try to open it from the webdynpro perspective:

Plugin Name: Metamodel Core
Plugin ID: com.sap.ide.metamodel.core
Class: com.sap.ide.metamodel.core.plugin.MetamodelManager
Method: getJavaProjectClassPaths
Message: project has no Java Nature. projectName =  Welcome
Exception: org.eclipse.core.internal.resources.ResourceException: 
  Missing project nature class for org.eclipse.jdt.core.javanature.

I'm using jdk1.5.0_09.

Any ideas about this error?

Regards,