ZD advised me to upgrade to v1.0. So I did. All is well and the Calendar even seemed to finish sync all my events, but when it was done I got an exception + stack trace. Subsequent attempts to refresh the calendar thereafter give me the error, and validation also fails telling me I need to upgrade when I already have. Any ideas?

Your Yahoo! account doesn't support calendar. Please either upgrade to add the support or turn off calendar sync option.

Debug message: must upgrade to all-new yahoo calendar service

Exception:

com.zimbra.cs.mailbox.OfflineServiceException: must upgrade to all-new yahoo calendar service
ExceptionId:btpool0-5:1243620974357:1b715464bac5f887
Codeffline.YCALDAV_NEED_UPGRADE
at com.zimbra.cs.mailbox.OfflineServiceException.YCAL DAV_NEED_UPGRADE(OfflineServiceException.java:96)
at com.zimbra.cs.offline.OfflineCalDavDataImport.doCa lDavFailures(OfflineCalDavDataImport.java:66)
at com.zimbra.cs.offline.OfflineCalDavDataImport.impo rtData(OfflineCalDavDataImport.java:57)
at com.zimbra.cs.offline.OfflineImport.importData(Off lineImport.java:88)
at com.zimbra.cs.offline.YMailImport.importData(YMail Import.java:66)
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:275)
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)

If issue persists please post description and debug information here.