i get an error while dealing with the ejb project

ie
"IWAE0010E run-time exception java.lang.ClassCastException occured during validation.The validator being run was EJB validator and the message thrown was
org.eclipse.wst.common.componentcore.internal.ModuleStructuralModel cannot be cast to org.eclipse.wst.common.componentcore.internal.ArtifactEditModel"

the above message is displayed in a message box
with a heading EJB validator

i deleted and created a new EJB project
yet the same error is showing

1)tell me how to prevent this.
2)tell me how to create a build file for a ejb project
3)also tell me how to create a build file for my web project
(i have a web and ejb project
the web project has a jsp file named myemployee.jsp
it should call the ejb files which are stored in my ejb project)