Anytime I hit Send/Receive, I get the message 'Failure communicating with remote server. Please try again later.' But it still seems to be sending and receiving messages. Here are the details:

Debug message: HTTP request failed: 999: null

Exception:

com.zimbra.common.service.ServiceException: system failure: Yahoo address book synchronization failed
ExceptionId:btpool0-2:1235596771953:ba3a0d25013b02dc
Code:service.FAILURE
at com.zimbra.common.service.ServiceException.FAILURE (ServiceException.java:253)
at com.zimbra.cs.mailbox.SyncExceptionHandler.checkRe coverableException(SyncExceptionHandler.java:40)
at com.zimbra.cs.offline.ab.yab.YabImport.importData( YabImport.java:78)
at com.zimbra.cs.offline.YMailImport.importData(YMail Import.java:94)
at com.zimbra.cs.datasource.DataSourceManager.importD ata(DataSourceManager.java:154)
at com.zimbra.cs.mailbox.LocalMailbox.importData(Loca lMailbox.java:417)
at com.zimbra.cs.mailbox.LocalMailbox.syncAllLocalDat aSources(LocalMailbox.java:389)
at com.zimbra.cs.mailbox.LocalMailbox.sync(LocalMailb ox.java:431)
at com.zimbra.cs.service.offline.OfflineSync.handle(O fflineSync.java:49)
at com.zimbra.soap.SoapEngine.dispatchRequest(SoapEng ine.java:429)
at com.zimbra.soap.SoapEngine.dispatch(SoapEngine.jav a:286)
at com.zimbra.soap.SoapEngine.dispatch(SoapEngine.jav a:160)
at com.zimbra.soap.SoapServlet.doPost(SoapServlet.jav a:269)
at javax.servlet.http.HttpServlet.service(HttpServlet .java:727)
at com.zimbra.cs.servlet.ZimbraServlet.service(Zimbra Servlet.java:190)
at javax.servlet.http.HttpServlet.service(HttpServlet .java:820)
at org.mortbay.jetty.servlet.ServletHolder.handle(Ser vletHolder.java:487)
at org.mortbay.jetty.servlet.ServletHandler.handle(Se rvletHandler.java:362)
at org.mortbay.jetty.security.SecurityHandler.handle( SecurityHandler.java:216)
at org.mortbay.jetty.servlet.SessionHandler.handle(Se ssionHandler.java:181)
at org.mortbay.jetty.handler.ContextHandler.handle(Co ntextHandler.java:716)
at org.mortbay.jetty.webapp.WebAppContext.handle(WebA ppContext.java:406)
at org.mortbay.jetty.handler.ContextHandlerCollection .handle(ContextHandlerCollection.java:211)
at org.mortbay.jetty.handler.HandlerCollection.handle (HandlerCollection.java:114)
at org.mortbay.jetty.handler.HandlerWrapper.handle(Ha ndlerWrapper.java:139)
at org.mortbay.jetty.handler.RewriteHandler.handle(Re writeHandler.java:176)
at org.mortbay.jetty.handler.HandlerWrapper.handle(Ha ndlerWrapper.java:139)
at org.mortbay.jetty.Server.handle(Server.java:313)
at org.mortbay.jetty.HttpConnection.handleRequest(Htt pConnection.java:506)
at org.mortbay.jetty.HttpConnection$RequestHandler.co ntent(HttpConnection.java:844)
at org.mortbay.jetty.HttpParser.parseNext(HttpParser. java:644)
at org.mortbay.jetty.HttpParser.parseAvailable(HttpPa rser.java:211)
at org.mortbay.jetty.HttpConnection.handle(HttpConnec tion.java:381)
at org.mortbay.io.nio.SelectChannelEndPoint.run(Selec tChannelEndPoint.java:396)
at org.mortbay.thread.BoundedThreadPool$PoolThread.ru n(BoundedThreadPool.java:442)
Caused by: com.zimbra.common.service.ServiceException: system failure: Contact sync error
ExceptionId:btpool0-2:1235596771953:ba3a0d25013b02dc
Code:service.FAILURE
at com.zimbra.common.service.ServiceException.FAILURE (ServiceException.java:253)
at com.zimbra.cs.offline.ab.yab.SyncSession.sync(Sync Session.java:87)
at com.zimbra.cs.offline.ab.yab.YabImport.importData( YabImport.java:76)
... 32 more
Caused by: org.apache.commons.httpclient.HttpException: HTTP request failed: 999: null
at com.zimbra.cs.offline.util.yab.Request.sendRequest (Request.java:91)
at com.zimbra.cs.offline.util.yab.Request.send(Reques t.java:55)
at com.zimbra.cs.offline.util.yab.SyncRequest.send(Sy ncRequest.java:79)
at com.zimbra.cs.offline.ab.yab.SyncSession.syncData( SyncSession.java:102)
at com.zimbra.cs.offline.ab.yab.SyncSession.sync(Sync Session.java:85)
... 33 more


Running Yahoo! Zimbra Desktop 1.0 (build 1482) on an Intel Mac OS X 10.4.11