Error reading XMLStreamReader.

Hi there,
I am implementing a STS and got the following exception with
username/password sending to issue a token.

The request looks like this:
<soapenv:Envelope xmlns:soapenv="http://schemas.xmlsoap.org/soap/envelope/"
xmlns:wst="http://schemas.xmlsoap.org/ws/2005/02/trust">
<soap:Header>
<wsse:Security
xmlns:wsse="http://docs.oasis-open.org/wss/2004/01/oasis-200401-wss-wssecurity-secext-1.0.xsd">
<wsse:UsernameToken
xmlns:wsse="http://docs.oasis-open.org/wss/2004/01/oasis-200401-wss-wssecurity-secext-1.0.xsd"
xmlns:bipro="http://www.bipro.net/namespace">
<wsse:Username>alice</wsse:Username>
<wsse:Password
Type="http://docs.oasis-open.org/wss/2004/01/oasis-200401-wss-387
username-token-profile-1.0#PasswordText">clarinet</wsse:Password>
</wsse:UsernameToken>
</wsse:Security>
</soap:Header>
<soapenv:Body
xmlns:wsu="http://docs.oasis-open.org/wss/2004/01/oasis-200401-wss-wssecurity-utility-1.0.xsd">
<wst:RequestSecurityToken>
<wst:TokenType>http://schemas.xmlsoap.org/ws/2005/02/sc/sct</wst:TokenType>

<wst:RequestType>http://schemas.xmlsoap.org/ws/2005/02/trust/Issue</wst:RequestType>
</wst:RequestSecurityToken>
</soapenv:Body>
</soapenv:Envelope>

The response:
<soap:Envelope xmlns:soap="http://schemas.xmlsoap.org/soap/envelope/">
<soap:Body>
<soap:Fault>
<faultcode>soap:Client</faultcode>
<faultstring>Error reading XMLStreamReader.</faultstring>
</soap:Fault>
</soap:Body>
</soap:Envelope>

Is there anybody who knows this problem and could give me a hint where to
fix?

Thanks,
SRog