Had to reset the sync data for an Entourage user (long story). Told it to delete the data on the server and use what is local.

Zimbra goes about gathering information, prompts to delete all address book data, and then calendar data from the server. Click ok both times. 5 minutes latter prompted again, then again, then again.

Pulled this out of the local sync.log on the mac:

Code:
[Mon Jun 11 14:31:39 200] incoming reply ==> <?xml version="1.0"?><soap:Envelope xmlns:soap="http://www.w3.org/2003/05/soap-envelope"><soap:Header><context xmlns="urn:zimbra"><sessionId id="184497">184497</sessionId><change token="28935"></change></context></soap:Header><soap:Body><SyncResponse xmlns="urn:zimbraMail" md="1181586695" token="28935" s="1784635871"><folder ms="27564" md="1180768801" color="0" u="0" f="" url="" n="0" id="11"><acl></acl><folder view="conversation" ms="27564" md="1180768801" color="0" u="0" f="" url="" n="0" l="11" name="Conversations" id="9"><acl></acl></folder><folder view="tag" ms="27564" md="1180768801" color="0" u="0" f="" url="" n="0" l="11" name="Tags" id="8"><acl></acl><tag d="1180560734000" ms="27564" md="1180768801" color="0" u="0" name="Medical" id="71" rev="25484"></tag><tag d="1180560691000" ms="27564" md="1180768801" color="0" u="0" name="Business" id="70" rev="25365"></tag><tag d="1180560679000" ms="27564" md="1180768801" color="0" u="0" name="Venture" id="69" rev="25333"></tag><tag d="1180560676000" ms="27564" md="1180768801" color="0" u="0" name="Auspice" id="68" rev="25327"></tag><tag d="1180560672000" ms="27564" md="1180768801" color="0" u="0" name="Unfiled" id="67" rev="25315"></tag><tag d="1180560667000" ms="27564" md="1180768801" color="0" u="0" name="Holiday Cards" id="65" rev="25294"></tag><tag d="1180560667000" ms="27564" md="1180768801" color="0" u="0" name="Travel" id="66" rev="25297"></tag><tag d="1178678131000" ms="27564" md="1180768801" color="0" u="0" name="Personal" id="64" rev="21899"></tag></folder><folder ms="27564" md="1180768801" color="0" u="0" f="" url="" n="0" l="11" name="USER_ROOT" id="1"><acl></acl><folder view="appointment" ms="28520" md="1181232845" color="1" u="0" f="#" rest="https://po.auspicecorp.com/home/sbirer/Calendar/" url="" n="0" l="1" name="Calendar" id="10"><acl></acl></folder><folder view="message" ms="27564" md="1180768801" color="0" u="0" f="" url="" n="0" l="1" name="Chats" id="14"><acl></acl></folder><folder view="contact" ms="27564" md="1180768801" color="0" u="0" f="" rest="https://po.auspicecorp.com/home/sbirer/Contacts/" url="" n="0" l="1" name="Contacts" id="7"><acl></acl></folder><folder view="message" ms="27564" md="1180768801" color="0" u="0" f="*" url="" n="8871" l="1" name="Deleted Items" id="266"><acl></acl><m 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8343,8336,8337,8335,8339,8340,8330,8329,8328,8334,8333,8326,8325,8332,8331,8324,8323,8320,8319,9292,8318,8317,8314,8316,8315,8322,8368,9289,8313,8312,8311,8310,8308,8307,8304,8302,8301,8300,8298,8306,8297,8299,8305,8296,8295,8294,8292,8291,10068,8289,8290,8288,8285,8286,8281,8279,8277,8276,8270,8269,8268,8267,10069,8265,8264,8272,8271,8274,8275,8263,8262,8259,8260,8261,8258,8257,8254,8253,8255,8256,9293,8252,8251,8287,9494,8250,8278,8249,8248,8247,9294,8246,8389,10070,8494,8284,8242,8245,8244,8241,8239,8236,8237,8240,8282,8238,8235,8233,8232,8231,8228,8230,8222,8223,8225,8226,8227,8221,8234,8220,8219,8218,8217,8216,8215,8214,8211,8213,8212,8208,8207,8209,8206,8205,8202,8203,8198,8197,8196,8195,8160,8210,8155,8159,8158,8153,8154,8152,8156,9305,8157,8162,8161,8164,8163,8165,8149,9306,8167,8150,8166,8151,8200,8381,9296,9953,9297,9298[assert] error: (null)
[assert] where: "ZimbraHelper_main.mm", "SyncCalendars", line: 1527