From an install of zdesktop_2_0_b10580_win32.msi, I was able to add a Zimbra account connecting to zcs-NETWORK-6.0.6_GA (patched) without any problem. When I added another Zimbra account connecting to zcs-6.0.7_GA_2470 (open source), it downloaded all of the mail and calendar events, but now it can't sync new messages. The error message follows:

Code:
Debug message: Java heap space

Exception:

java.lang.OutOfMemoryError: Java heap space
    at java.util.Arrays.copyOfRange(Unknown Source)
    at java.lang.String.(Unknown Source)
    at java.lang.StringBuilder.toString(Unknown Source)
    at net.fortuna.ical4j.data.CalendarParserImpl.parseProperty(CalendarParserImpl.java:263)
    at net.fortuna.ical4j.data.CalendarParserImpl.parsePropertyList(CalendarParserImpl.java:196)
    at net.fortuna.ical4j.data.CalendarParserImpl.parseComponent(CalendarParserImpl.java:355)
    at net.fortuna.ical4j.data.CalendarParserImpl.parsePropertyList(CalendarParserImpl.java:193)
    at net.fortuna.ical4j.data.CalendarParserImpl.parseCalendar(CalendarParserImpl.java:161)
    at net.fortuna.ical4j.data.CalendarParserImpl.parseCalendarList(CalendarParserImpl.java:133)
    at net.fortuna.ical4j.data.CalendarParserImpl.parse(CalendarParserImpl.java:94)
    at com.zimbra.cs.mailbox.calendar.ZCalendar$ZCalendarBuilder.parse(ZCalendar.java:920)
    at com.zimbra.cs.mailbox.calendar.ZCalendar$ZCalendarBuilder.buildMulti(ZCalendar.java:894)
    at com.zimbra.cs.mailbox.calendar.ZCalendar$ZCalendarBuilder.build(ZCalendar.java:878)
    at com.zimbra.cs.mime.handler.TextCalendarHandler.analyze(TextCalendarHandler.java:77)
    at com.zimbra.cs.mime.handler.TextCalendarHandler.getICalendar(TextCalendarHandler.java:52)
    at com.zimbra.cs.mime.ParsedMessage.analyzePart(ParsedMessage.java:1101)
    at com.zimbra.cs.mime.ParsedMessage.analyzeNonBodyParts(ParsedMessage.java:433)
    at com.zimbra.cs.mime.ParsedMessage.analyzeFully(ParsedMessage.java:467)
    at com.zimbra.cs.mailbox.CalendarItem.getIndexDocuments(CalendarItem.java:342)
    at com.zimbra.cs.mailbox.CalendarItem.generateIndexData(CalendarItem.java:218)
    at com.zimbra.cs.mailbox.IndexHelper.indexItemList(IndexHelper.java:848)
    at com.zimbra.cs.mailbox.IndexHelper.indexDeferredItemsInternal(IndexHelper.java:367)
    at com.zimbra.cs.mailbox.IndexHelper.indexDeferredItems(IndexHelper.java:284)
    at com.zimbra.cs.mailbox.IndexHelper.maybeIndexDeferredItems(IndexHelper.java:240)
    at com.zimbra.cs.mailbox.Mailbox.addMessage(Mailbox.java:4341)
    at com.zimbra.cs.mailbox.Mailbox.addMessage(Mailbox.java:4334)
    at com.zimbra.cs.mailbox.InitialSync.saveMessage(InitialSync.java:1207)
    at com.zimbra.cs.mailbox.InitialSync.syncMessagesAsTgz(InitialSync.java:1027)
    at com.zimbra.cs.mailbox.InitialSync.syncMessages(InitialSync.java:960)
    at com.zimbra.cs.mailbox.InitialSync.syncMessagelikeItems(InitialSync.java:433)
    at com.zimbra.cs.mailbox.InitialSync.initialFolderSync(InitialSync.java:323)
    at com.zimbra.cs.mailbox.InitialSync.prioritySync(InitialSync.java:397)