NPE exception raises when content picking

Here the exception I have after trying to create a linked copy through the content picking search of update/create page popup engine and nothing created consequently :

2009-03-24 17:02:51,328: ERROR [org.jahia.services.importexport.ImportExportBaseService] - Error during copying
java.lang.NullPointerException
at org.jahia.services.importexport.JahiaLegacyExporter.export(JahiaLegacyExporter.java:456)
at org.jahia.services.importexport.JahiaLegacyExporter.export(JahiaLegacyExporter.java:151)
at org.jahia.services.importexport.ImportExportBaseService.export(ImportExportBaseService.java:725)
at org.jahia.services.importexport.ImportExportBaseService.copy(ImportExportBaseService.java:1528)
at org.jahia.services.importexport.ImportExportBaseService.copy(ImportExportBaseService.java:1478)
at org.jahia.services.importexport.ImportExportBaseService$$FastClassByCGLIB$$de1c40f7.invoke(<generated>)
at net.sf.cglib.proxy.MethodProxy.invoke(MethodProxy.java:149)
at org.springframework.aop.framework.Cglib2AopProxy$CglibMethodInvocation.invokeJoinpoint(Cglib2AopProxy.java:700)
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:149)
at org.springframework.aop.interceptor.AbstractTraceInterceptor.invoke(AbstractTraceInterceptor.java:113)
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:171)
at org.springframework.aop.framework.Cglib2AopProxy$DynamicAdvisedInterceptor.intercept(Cglib2AopProxy.java:635)
at org.jahia.services.importexport.ImportExportBaseService$$EnhancerByCGLIB$$442365b6.copy(<generated>)
at org.jahia.services.importexport.CopyJob.executeJahiaJob(CopyJob.java:92)
at org.jahia.services.scheduler.BackgroundJob.execute(BackgroundJob.java:164)
at org.quartz.core.JobRunShell.run(JobRunShell.java:202)
at org.quartz.simpl.SimpleThreadPool$WorkerThread.run(SimpleThreadPool.java:525)