Why does package removal fail via 'System Set Manger' with error "Error scheduling package installations for event SsmRemovePackagesEvent" ?

Issue

• Package removal from Red Hat Satellite is not working via SSM(System Set Manager).

• Error in /var/log/tomcat6/catalina.out

2014-02-20 15:59:24,237 [RHN Message Dispatcher] ERROR com.redhat.rhn.frontend.events.SsmRemovePackagesAction - Error scheduling package installations for event SsmRemovePackagesEvent[SsmPackageEvent[userId=43, earliest=Thu Feb 20 15:59:24 IST 2014, before=false]]
java.lang.NullPointerException
    at com.redhat.rhn.frontend.events.SsmRemovePackagesAction.doSchedule(SsmRemovePackagesAction.java:97)
    at com.redhat.rhn.frontend.events.SsmPackagesAction.scheduleAction(SsmPackagesAction.java:166)
    at com.redhat.rhn.frontend.events.SsmPackagesAction.doExecute(SsmPackagesAction.java:86)
    at com.redhat.rhn.frontend.events.AbstractDatabaseAction.execute(AbstractDatabaseAction.java:47)
    at com.redhat.rhn.common.messaging.ActionExecutor.run(ActionExecutor.java:69)
    at com.redhat.rhn.common.messaging.MessageDispatcher.run(MessageDispatcher.java:58)
    at java.lang.Thread.run(Thread.java:761)