This is eclipse log.
!SESSION 2011-10-26 11:29:05.443 -
eclipse.buildId=M20110210-1200
java.version=1.6.0_20
java.vendor=Sun Microsystems Inc.
BootLoader constants: OS=win32, ARCH=x86_64, WS=win32, NL=es_ES
Framework arguments: -product org.eclipse.epp.package.jee.product C:\J2EE\jdk1.6.0_27\bin\javaw.exe openFile
Command-line arguments: -os win32 -ws win32 -arch x86_64 -product org.eclipse.epp.package.jee.product C:\J2EE\jdk1.6.0_27\bin\javaw.exe openFile
!ENTRY org.eclipse.core.resources 4 2 2011-10-26 11:29:31.375
!MESSAGE Problems occurred when invoking code from plug-in: "org.eclipse.core.resources".
!STACK 0
java.lang.NullPointerException
at org.eclipse.wst.validation.internal.model.FilterRule$ProjectNature.(ValManager.java:1074)
at org.eclipse.wst.validation.internal.ValManager$ValidatorProjectManager.get(ValManager.java:1092)
at org.eclipse.wst.validation.internal.ValManager.accept(ValManager.java:747)
at org.eclipse.wst.validation.internal.ValBuilderJob.finishingValidation(ValBuilderJob.java:161)
at org.eclipse.wst.validation.internal.ValBuilderJob.runInWorkspace(ValBuilderJob.java:131)
at org.eclipse.core.internal.resources.InternalWorkspaceJob.run(InternalWorkspaceJob.java:38)
at org.eclipse.core.internal.jobs.Worker.run(Worker.java:54)