<?xml version="1.0" encoding="utf-8"?>
<soap:Envelope xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:xsd="http://www.w3.org/2001/XMLSchema"
xmlns:soap="http://schemas.xmlsoap.org/soap/envelope/">
    <soap:Body>
        <UpdateListItems
xmlns="http://schemas.microsoft.com/sharepoint/soap/">
            <listName>Tasks</listName>
                <updates>
                    <Batch OnError="Continue" ListVersion="1">
                    <Method ID="1" Cmd="Update">
                        <Field Name="ID">199</Field>
                        <Field Name="AssignedTo">Joe</Field>
                    </Method>
                    </Batch>
                </updates>
        </UpdateListItems>
    </soap:Body>
</soap:Envelope>

Hi Eric,

for your information, I think there is nothing wrong with the
configurations.
The permission is correct, and the soap message looks good.

If you were using JQuery, you need to add the additional request header
"SOAPAction" shown in with following code sample:

$.ajax({
    url: Web Service URL,
    beforeSend: function(xhr) {
        xhr.setRequestHeader("SOAPAction",
        "http://schemas.microsoft.com/sharepoint/soap/UpdateListItems");
    },
    type: "POST",
    dataType: "xml",
    data: soapEnvelope,
    complete: processResult,
    contentType: "text/xml; charset=utf-8"

Get Secure! - www.microsoft.com/security
=====================================================
When responding to posts, please "Reply to Group" via your newsreader so
that others may learn and benefit from your issue.
=====================================================
This posting is provided "AS IS" with no warranties, and confers no rights.