We are using the LDAP sync widget for quite some time now and hardly encounter any issues. However this week (while nothing was changed on the Mendix/LDAP widget side) we encounter a non descriptive NULL error indicating that users cannot be synchronized. I am not really familiar with java programming, but managed to debug the error to the location in the code where the error occurs. The error occurs in the ImportUsers.java class and to be more specific in the following piece of code: //Remove roles belonging to groups that have been removed currentGroups.removeAll(newGroups); for(IMendixIdentifier removedGroup : currentGroups) roles.removeAll(groupByIdCache.get(removedGroup)); for(IMendixIdentifier newGroup : newGroups) roles.addAll(groupByIdCache.get(newGroup)); To be more precise in the part: roles.addAll(groupByIdCache.get(newGroup)); newGroup seems to be NULL in specific situation. In the Eclipse debug form I do see that newGroups does contain values. It seems to be related to specific LDAP groups however I do not know of any differences between the LDAP groups (and the LDAP admin indicates that nothing changed recently). Fact is that all was working fine till earlier this week and now it doesn't work anymore (no mendix side changes/no new deployment or anything like that). Hope anybody can assist in resolving this issue. Kind regards, Brian UPDATE: After extensive research we did not find the root cause (yet) and decided to purge all LDAP data stored in the database and redid the setup/configuration. This resolved the issue. Quite a workaround however and we would of course still be very interested in finding the root cause (also logged a call at Mendix support) error message and stacktrace: [0025][12:25:47] Failed to import user 'CN=XXX XXXX,OU=Users YYY,OU=ZZZ ,OU=RRRRR,DC=FFF,DC=local', skipping.. -------- java.lang.NullPointerException at java.util.ArrayList.addAll(ArrayList.java:472) at ldap.ImportUsers.processUserImport(ImportUsers.java:253) at ldap.ImportUsers$UserMapper.handleNameClassPair(ImportUsers.java:197) at org.springframework.ldap.core.LdapTemplate.search(LdapTemplate.java:297) at org.springframework.ldap.core.LdapTemplate.search(LdapTemplate.java:259) at ldap.LdapModule.pagedSearchHelper(LdapModule.java:241) at ldap.LdapModule.pagedSearch(LdapModule.java:226) at ldap.ImportUsers.importUsers(ImportUsers.java:122) at ldap.ImportUsers.runImportUsers(ImportUsers.java:63) at ldap.actions.ImportLdapUsers.executeAction(ImportLdapUsers.java:40) at ldap.actions.ImportLdapUsers.executeAction(ImportLdapUsers.java:1) at com.mendix.systemwideinterfaces.core.UserAction.execute(SourceFile:57) at com.mendix.core.actionmanagement.CoreAction.call(SourceFile:457) at hG.b(SourceFile:206) at com.mendix.core.Core.execute(SourceFile:226) at lp.a(SourceFile:69) at mz.a(SourceFile:77) at my.a(SourceFile:155) at my.executeAction(SourceFile:98) at com.mendix.systemwideinterfaces.core.UserAction.execute(SourceFile:57) at com.mendix.core.actionmanagement.CoreAction.call(SourceFile:457) at hG.b(SourceFile:206) at com.mendix.core.Core.executeSync(SourceFile:203) at lq.a(SourceFile:60) at mz.a(SourceFile:77) at my.a(SourceFile:155) at my.executeAction(SourceFile:98) at com.mendix.systemwideinterfaces.core.UserAction.execute(SourceFile:57) at com.mendix.core.actionmanagement.CoreAction.call(SourceFile:457) at hG.b(SourceFile:206) at com.mendix.core.Core.executeSync(SourceFile:203) at lU.a(SourceFile:60) at mz.a(SourceFile:77) at my.a(SourceFile:155) at my.executeAction(SourceFile:98) at com.mendix.systemwideinterfaces.core.UserAction.execute(SourceFile:57) at hH.execute(SourceFile:27) at com.mendix.core.actionmanagement.CoreAction.call(SourceFile:457) at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:303) at java.util.concurrent.FutureTask.run(FutureTask.java:138) at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:895) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:918) at java.lang.Thread.run(Thread.java:662)