Just installed Zimbra Desktop yesterday. Tested with my Yahoo Mail account. At first it asked me to update to the new calendar, which I did. Then It synced my account. Mail was synced, Contacts were synced but Calendar waqs not. I received the following error message:

Failure communicating with remote server. Please try again later.

Debug message: Expected [-3], read [-1] at line 1

Exception:

com.zimbra.common.service.ServiceException: parse error: Caught ParseException parsing calendar: net.fortuna.ical4j.data.ParserException: Expected [-3], read [-1] at line 1

ExceptionId:mid=4:1241350895664:e547eeb663900ae8
Code:service.PARSE_ERROR
at com.zimbra.common.service.ServiceException.PARSE_E RROR(ServiceException.java:271)
at com.zimbra.cs.mailbox.calendar.ZCalendar$ZCalendar Builder.parse(ZCalendar.java:1051)
at com.zimbra.cs.mailbox.calendar.ZCalendar$ZCalendar Builder.buildMulti(ZCalendar.java:1007)
at com.zimbra.cs.mailbox.calendar.ZCalendar$ZCalendar Builder.build(ZCalendar.java:991)
at com.zimbra.cs.datasource.CalDavDataImport.applyRem oteItem(CalDavDataImport.java:413)
at com.zimbra.cs.datasource.CalDavDataImport.sync(Cal DavDataImport.java:497)
at com.zimbra.cs.datasource.CalDavDataImport.importDa ta(CalDavDataImport.java:77)
at com.zimbra.cs.offline.OfflineCalDavDataImport.impo rtData(OfflineCalDavDataImport.java:53)
at com.zimbra.cs.offline.OfflineImport.importData(Off lineImport.java:88)
at com.zimbra.cs.offline.YMailImport.importData(YMail Import.java:56)
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.mailbox.LocalMailbox.syncOnTimer(Loc alMailbox.java:361)
at com.zimbra.cs.mailbox.DesktopMailbox$1.run(Desktop Mailbox.java:436)
at java.util.TimerThread.mainLoop(Unknown Source)
at java.util.TimerThread.run(Unknown Source)
Caused by: net.fortuna.ical4j.data.ParserException: Expected [-3], read [-1] at line 1
at net.fortuna.ical4j.data.CalendarParserImpl.assertT oken(CalendarParserImpl.java:395)
at net.fortuna.ical4j.data.CalendarParserImpl.assertT oken(CalendarParserImpl.java:435)
at net.fortuna.ical4j.data.CalendarParserImpl.parseCa lendarList(CalendarParserImpl.java:141)
at net.fortuna.ical4j.data.CalendarParserImpl.parse(C alendarParserImpl.java:100)
at com.zimbra.cs.mailbox.calendar.ZCalendar$ZCalendar Builder.parse(ZCalendar.java:1023)
... 16 more

If issue persists please post description and debug information here.