WebService Payload Truncated (#2006 Out of Bounds Error) on Send

I have a problem sending a large base64Binary parameter as part of a SOAP body
using Gumbo build 9127. The payload generated by Flex to be sent looks like
this (truncated for brevity):

<SOAP-ENV:Envelope xmlns:SOAP-ENV="http://schemas.xmlsoap.org/soap/envelope/"
xmlns:xsd="http://www.w3.org/2001/XMLSchema"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
<SOAP-ENV:Body
SOAP-ENV:encodingStyle="http://schemas.xmlsoap.org/soap/encoding/">
<tns:mLoadCalibration xmlns:tns="x.com">
<pFileName
xsi:type="xsd:string">SCANNER_374_090511_1201_full.cal</pFileName>
<pFileContent
xsi:type="xsd:base64Binary">AABAQAAAu0MAAAzCMxEPwtSDDsKjRonCAAAWQ3JQtDwK1yM8eFMf\
vArX...IXD3uCWusQSh70AkBpBAPAbRpZjHEbNzKxAXE+tQA==</pFileContent>
</tns:mLoadCalibration>
</SOAP-ENV:Body>
</SOAP-ENV:Envelope>

Before the entire payload is sent, my responder fault handler is receiving an
"Error #2006: The supplied index is out of bounds.". The responder result
handler is shortly after triggered, with the result form the web service.

Looking at the raw data sent over the wire using Wireshark, I was able to see
that Flex is truncating on send the contents of the parameter (pFileContent),
but then completing the send of the remainder of the payload. Here is an
example of what the received data looked like (note the truncation of the
pFileContent element)

<SOAP-ENV:Envelope xmlns:SOAP-ENV="http://schemas.xmlsoap.org/soap/envelope/"
xmlns:xsd="http://www.w3.org/2001/XMLSchema"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
<SOAP-ENV:Body
SOAP-ENV:encodingStyle="http://schemas.xmlsoap.org/soap/encoding/">
<tns:mLoadCalibration xmlns:tns="x.com">
<pFileName
xsi:type="xsd:string">SCANNER_374_090511_1201_full.cal</pFileName>
<pFileContent
xsi:type="xsd:base64Binary">AABAQAAAu0MAAAzCMxEPwtSDDsKjRonCAAAWQ3JQtDwK1yM8eFMf\
vArX...IXD
</tns:mLoadCalibration>
</SOAP-ENV:Body>
</SOAP-ENV:Envelope>

Please see attached file for complete generated SOAP envelope by Flex. Note that it is okay, but gets truncated on send.