1564910 - Cannot start plug-in error in Java NWA

While trying to configure SSO on a JAVA server using SAP Netweaver Administrator (http://<server>:port/nwa) -> System Management -> Configuration -> Trusted Systems, the operation fails and the below error is logged in the trace file (default trace):

com.sap.lm.webadmin.mainframe.MainFrameView#J2EE_ADMIN#SAPEngine_Application_Thread#Error##Java###Cannot start plug-in.[EXCEPTION]com.sap.engine.services.jmx. exception.MBeanServerCluster Exception:Exception during invocation of remote MBeanServer method, target node Exception while loading class:com.sapportals.supportplatform.plugins.java.lang.NoClassDefFound Error:Caused by: java.lang.ClassNotFoundException:Found in negative cache.

SAP NETWEAVER JAVA WEB APPLICATION SERVER 6.40 and 7.00

inconsistency, ticket, strustsso, wizard ,SAP Production ABAP R/3 ERP SRM CRM ERP PPM SEM APO XI PI PORTAL Test development QA, SSO tool 1083421 SDM force option LM-TOOLS SAP-JTECHS SAP-JTECHF , KBA , BC-NWA-JEE , J2EE Integration Plugins , BC-JAS-COR , Enterprise Runtime, Core J2EE Framework , Problem