jdbc driver question

I use the jdbc driver to synchronize data to sql2000 error, suggesting that the lack of a primary key value, but I directly insert data in the database can be inserted, then I update this data through the jdbc driver can be successful,please tell me why? thanks!
log infomation:

DirXML Log Event -------------------
Driver: \IDTREE\services\IdTreeDriverSet2\ID_to_XJLL
Channel: Subscriber
Object: \IDTREE\abc\00000010
Status: Error
Message: <description>Unable to add object. Unable to retrieve primary key value(s) from event. Event missing required value for primary key column 'T_IDM_USER.Usercode'.</description
>
<object-dn>O=abc\CN=00000010</object-dn>
<jdbc:document xml:space="preserve" xmlns:jdbc="urn:dirxml:jdbc">&lt;nds dtdversion="3.5" ndsversion="8.x">
&lt;source>
&lt;product version="4.0.0">DirXML&lt;/product>
&lt;contact>Novell, Inc.&lt;/contact>
&lt;/source>
&lt;input>
&lt;add cached-time="20120207020635.368Z" class-name="T_IDM_USER" event-id="services#20120207020635#99#1:a1ea82e5-9139-4eda-848f-e582eaa13991" qualified-src-dn="O=abc\CN=000
00010" src-dn="\IDTREE\abc\00000010" src-entry-id="256713" timestamp="0#0">
&lt;add-attr attr-name="Usercode">
&lt;value naming="true" timestamp="1317262722#22" type="string">00000010&lt;/value>
&lt;/add-attr>
&lt;add-attr attr-name="Fullname">
&lt;value timestamp="1317262722#6" type="string">wanghua&lt;/value>
&lt;/add-attr>
&lt;add-attr attr-name="Password">
&lt;value>E10ADC3949BA59ABBE56E057F20F883E&lt;/value>
&lt;/add-attr>
&lt;add-attr attr-name="USERSTATE">
&lt;value type="string">1&lt;/value>
&lt;/add-attr>
&lt;/add>