While adding plugins, the log files shows  org.xml.sax.SAXParseException: Premature end of file. exception.
There is no detail as to which module is causing the problem.
Verified the nbms for illegally formed XML files and could not find any. 
I can provide with nbms which are displaying the behavior.

[Fatal Error] :-1:-1: Premature end of file.
[Fatal Error] :-1:-1: Premature end of file.
INFO [org.netbeans.modules.apisupport.project]: org.xml.sax.SAXParseException: Premature end of file.
org.xml.sax.SAXParseException: Premature end of file.
	at com.sun.org.apache.xerces.internal.parsers.DOMParser.parse(DOMParser.java:264)
	at com.sun.org.apache.xerces.internal.jaxp.DocumentBuilderImpl.parse(DocumentBuilderImpl.java:292)
	at org.openide.xml.XMLUtil.parse(XMLUtil.java:329)
	at org.netbeans.modules.apisupport.project.universe.ModuleList.findBinaryNBMFiles(ModuleList.java:753)
Caused: java.io.IOException
	at org.netbeans.modules.apisupport.project.universe.ModuleList.findBinaryNBMFiles(ModuleList.java:756)
	at org.netbeans.modules.apisupport.project.universe.ModuleList.createModuleListFromBinaries
(ModuleList.java:730)
	at org.netbeans.modules.apisupport.project.universe.ModuleList.findOrCreateModuleListFromBinaries
(ModuleList.java:670)
	at org.netbeans.modules.apisupport.project.universe.ModuleList.findOrCreateModuleListFromSuite
(ModuleList.java:561)
	at org.netbeans.modules.apisupport.project.universe.ModuleList$1.run(ModuleList.java:177)
	at org.netbeans.modules.apisupport.project.universe.ModuleList$1.run(ModuleList.java:157)
	at org.openide.util.Mutex.readAccess(Mutex.java:327)
	at org.openide.util.Mutex$1R.run(Mutex.java:1299)
	at org.openide.util.Mutex.doWrapperAccess(Mutex.java:1318)
	at org.openide.util.Mutex.readAccess(Mutex.java:320)
	at org.netbeans.modules.apisupport.project.universe.ModuleList.getModuleList(ModuleList.java:156)
	at org.netbeans.modules.apisupport.project.NbModuleProject.getModuleList(NbModuleProject.java:517)
[catch] at org.netbeans.modules.apisupport.project.Evaluator$2.run(Evaluator.java:222)
	at org.netbeans.modules.apisupport.project.Evaluator$2.run(Evaluator.java:219)
	at org.openide.util.Mutex.readAccess(Mutex.java:327)
	at org.openide.util.Mutex$1R.run(Mutex.java:1299)
	at org.openide.util.Mutex.doWrapperAccess(Mutex.java:1318)
	at org.openide.util.Mutex.readAccess(Mutex.java:275)
	at org.netbeans.modules.apisupport.project.Evaluator.reset(Evaluator.java:218)
	at org.netbeans.modules.apisupport.project.Evaluator.access$100(Evaluator.java:95)
	at org.netbeans.modules.apisupport.project.Evaluator$1.run(Evaluator.java:206)
	at org.netbeans.modules.apisupport.project.Evaluator$1.run(Evaluator.java:203)
	at org.openide.util.Mutex.readAccess(Mutex.java:327)
	at org.openide.util.Mutex$1R.run(Mutex.java:1299)
	at org.netbeans.api.project.ProjectManager$2$1.run(ProjectManager.java:120)
	at org.openide.filesystems.EventControl.runAtomicAction(EventControl.java:120)
	at org.openide.filesystems.FileSystem.runAtomicAction(FileSystem.java:499)
	at org.openide.filesystems.FileUtil.runAtomicAction(FileUtil.java:215)
	at org.netbeans.api.project.ProjectManager$2.execute(ProjectManager.java:118)
	at org.openide.util.Mutex.doWrapperAccess(Mutex.java:1320)
	at org.openide.util.Mutex.readAccess(Mutex.java:275)
	at org.netbeans.modules.apisupport.project.Evaluator.delegatingEvaluator(Evaluator.java:202)
	at org.netbeans.modules.apisupport.project.Evaluator.getProperty(Evaluator.java:152)
	at org.netbeans.spi.java.project.classpath.support.ProjectClassPathImplementation.getPath
(ProjectClassPathImplementation.java:135)
	at org.netbeans.spi.java.project.classpath.support.ProjectClassPathImplementation.<init>
(ProjectClassPathImplementation.java:87)
	at 
org.netbeans.spi.java.project.classpath.support.ProjectClassPathSupport.createPropertyBasedClassPathImplementation
(ProjectClassPathSupport.java:73)
	at org.netbeans.modules.apisupport.project.queries.ClassPathProviderImpl.createPathFromProperty
(ClassPathProviderImpl.java:225)
	at org.netbeans.modules.apisupport.project.queries.ClassPathProviderImpl.createCompileClasspath
(ClassPathProviderImpl.java:231)
	at org.netbeans.modules.apisupport.project.queries.ClassPathProviderImpl.findClassPath
(ClassPathProviderImpl.java:117)
	at org.netbeans.modules.apisupport.project.queries.ClassPathProviderImpl.getProjectClassPaths
(ClassPathProviderImpl.java:353)
	at org.netbeans.modules.apisupport.project.NbModuleProject.open(NbModuleProject.java:710)
	at org.netbeans.modules.apisupport.project.NbModuleProject$OpenedHook.projectOpened(NbModuleProject.java:661)
	at org.netbeans.spi.project.ui.ProjectOpenedHook$1.projectOpened(ProjectOpenedHook.java:81)
	at org.netbeans.spi.project.ui.support.UILookupMergerSupport$OpenHookImpl.projectOpened
(UILookupMergerSupport.java:193)
	at org.netbeans.spi.project.ui.ProjectOpenedHook$1.projectOpened(ProjectOpenedHook.java:81)
	at org.netbeans.modules.project.ui.OpenProjectList.notifyOpened(OpenProjectList.java:926)
	at org.netbeans.modules.project.ui.OpenProjectList.access$800(OpenProjectList.java:123)
	at org.netbeans.modules.project.ui.OpenProjectList$LoadOpenProjects.loadOnBackground(OpenProjectList.java:335)
	at org.netbeans.modules.project.ui.OpenProjectList$LoadOpenProjects.run(OpenProjectList.java:260)
	at org.openide.util.RequestProcessor$Task.run(RequestProcessor.java:561)
	at org.openide.util.RequestProcessor$Processor.run(RequestProcessor.java:986)