i nearly had the same problem, but i had some errors in error.log: the error occured every time a user signed on, and at that time the error is duplicated for every user in the ldap database.so every login produces about 30 errors on my error.log.
2007.09.07 16:12:21 org.jivesoftware.openfire.ldap.LdapGroupProvider.populateGroups(LdapGroupProvid er.java:679)
javax.naming.InvalidNameException: Invalid name: lastname_firstname
at javax.naming.ldap.Rfc2253Parser.doParse(Rfc2253Parser.java:86)
at javax.naming.ldap.Rfc2253Parser.parseDn(Rfc2253Parser.java:45)
at javax.naming.ldap.LdapName.parse(LdapName.java:772)
at javax.naming.ldap.LdapName.<init>(LdapName.java:108)
at org.jivesoftware.openfire.ldap.LdapGroupProvider.populateGroups(LdapGroupProvid er.java:663)
at org.jivesoftware.openfire.ldap.LdapGroupProvider.getGroup(LdapGroupProvider.jav a:99)
at org.jivesoftware.openfire.group.GroupManager.getGroup(GroupManager.java:184)
at org.jivesoftware.openfire.roster.RosterItem.getSharedGroups(RosterItem.java:391 )
at org.jivesoftware.openfire.roster.Roster.getReset(Roster.java:521)
at org.jivesoftware.openfire.handler.IQRosterHandler.manageRoster(IQRosterHandler. java:202)
at org.jivesoftware.openfire.handler.IQRosterHandler.handleIQ(IQRosterHandler.java :105)
at org.jivesoftware.openfire.handler.IQHandler.process(IQHandler.java:48)
at org.jivesoftware.openfire.IQRouter.handle(IQRouter.java:300)
at org.jivesoftware.openfire.IQRouter.route(IQRouter.java:104)
at org.jivesoftware.openfire.spi.PacketRouterImpl.route(PacketRouterImpl.java:67)
at org.jivesoftware.openfire.net.StanzaHandler.processIQ(StanzaHandler.java:289)
at org.jivesoftware.openfire.net.ClientStanzaHandler.processIQ(ClientStanzaHandler .java:79)
at org.jivesoftware.openfire.net.StanzaHandler.process(StanzaHandler.java:254)
at org.jivesoftware.openfire.net.StanzaHandler.process(StanzaHandler.java:153)
at org.jivesoftware.openfire.nio.ConnectionHandler.messageReceived(ConnectionHandl er.java:132)
at org.apache.mina.common.support.AbstractIoFilterChain$TailFilter.messageReceived (AbstractIoFilterChain.java:703)
at org.apache.mina.common.support.AbstractIoFilterChain.callNextMessageReceived(Ab stractIoFilterChain.java:362)
at org.apache.mina.common.support.AbstractIoFilterChain.access$1100(AbstractIoFilt erChain.java:54)
at org.apache.mina.common.support.AbstractIoFilterChain$EntryImpl$1.messageReceive d(AbstractIoFilterChain.java:800)
at org.apache.mina.filter.codec.support.SimpleProtocolDecoderOutput.flush(SimplePr otocolDecoderOutput.java:62)
at org.apache.mina.filter.codec.ProtocolCodecFilter.messageReceived(ProtocolCodecF ilter.java:200)
at org.apache.mina.common.support.AbstractIoFilterChain.callNextMessageReceived(Ab stractIoFilterChain.java:362)
at org.apache.mina.common.support.AbstractIoFilterChain.access$1100(AbstractIoFilt erChain.java:54)
at org.apache.mina.common.support.AbstractIoFilterChain$EntryImpl$1.messageReceive d(AbstractIoFilterChain.java:800)
at org.apache.mina.filter.executor.ExecutorFilter.processEvent(ExecutorFilter.java :266)
at org.apache.mina.filter.executor.ExecutorFilter$ProcessEventsRunnable.run(Execut orFilter.java:326)
at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java: 650)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:675)
at java.lang.Thread.run(Thread.java:595)
i noticed the error i think after i changed from active directory to openldap on gentoo linux.
but then I changed the following setting it worked again:
server settings ->profile settings -> change the ldap options on the third page with the groups, i enabled posix on this page and it worked. do restart after that change, i think it could help
please tell if it worked