DownloadFilePart - SAXException

[Anonymous]

Problem: We need to download a file from vault, (previously used DocumentService.downloadFile(...) ) and do not have access to the VDF.AcquireFiles method.  

Background: I am using wsdl2java generator to get the vault sdk classes. I can login to vault, get file information, etc. using this approach.

Calling FilestoreService.DownloadFilePart( byte[] downloadTicket, long firstByte, long lastByte, boolean allowSync) results in the SAXException shown above, with the stack trace:

org.xml.sax.SAXException: Found character data inside an array element while deserializing
	at org.apache.axis.encoding.ser.ArrayDeserializer.characters(ArrayDeserializer.java:502)
	at org.apache.axis.encoding.DeserializationContext.characters(DeserializationContext.java:966)
	at org.apache.axis.message.SAX2EventRecorder.replay(SAX2EventRecorder.java:177)
	at org.apache.axis.message.MessageElement.publishToHandler(MessageElement.java:1141)
	at org.apache.axis.message.RPCElement.deserialize(RPCElement.java:236)
	at org.apache.axis.message.RPCElement.getParams(RPCElement.java:384)
	at org.apache.axis.client.Call.invoke(Call.java:2467)
	at org.apache.axis.client.Call.invoke(Call.java:2366)
	at org.apache.axis.client.Call.invoke(Call.java:1812)
	at AutodeskDM.Filestore.Filestore._1._22._2015.FilestoreServiceSoapStub.downloadFilePart(FilestoreServiceSoapStub.java:587)

the function call is:

ByteArray[] ba = vaultDocumentService.getDownloadTicketsByFileIds((long[])fileToDownload.getId());
allowSync = false;				
vaultFilestoreService.downloadFilePart(ba[0].getBytes(), (long)0, fileToDownload.getFileSize()-1, allowSync);

I can inspect each element (ba, file id) and see that the elements are populated and the right information is referenced. I have isolated the problem to the downloadTicket parameter that I am passing, but I can inspect the downloadTicket I am passing and everything seems to look right, assuming getDownloadTicketByFileIds is returning the right thing.

Any ideas what is going on here?  Or ideas to try??