Vault 2014 SOAP Response 400

[lsimons1]

We made a document viewer application utilizing the Vault SOAP API back on Vault 2013.  The following SOAP operation no longer receives a correct response:

<?xml version="1.0" encoding="UTF-8"?>
<soap:Envelope xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:soap="http://schemas.xmlsoap.org/soap/envelope/">
<soap:Body>
<SignInReadOnly xmlns="http://AutodeskDM/Services/Security/1/20/2011/">
<userName>my_user</userName>
<userPassword/>
<knowledgeVault>SFIC_Vault</knowledgeVault>
</SignInReadOnly>
</soap:Body>
</soap:Envelope>

It seems identical to what used to work and is similar to working operations I've seen on the forum.  It seems to occur universally for all calls we make except to the InformationService.  Are there any changes in Vault 2014 that would make this behaviour expected?  Unfortunately, this has knocked our whole app offline.

Thanks,

Louis