[RPC Fault faultString="Error #1090: XML parser failure: element is malformed." faultCode="Client.CouldNotDecode" faultDetail="null"]

I get the following error message when I try to perform an update in flash builder 4 beta:

[RPC Fault faultString="Error #1090: XML parser failure: element is malformed." faultCode="Client.CouldNotDecode" faultDetail="null"]
at mx.rpc.http::AbstractOperation/http://www.adobe.com/2006/flex/mx/internal::processResult()[E:\dev\gumbo_beta2\frameworks\projects\rpc\src\mx\rpc\http\AbstractOperation.as:1022]
at mx.rpc::AbstractInvoker/http://www.adobe.com/2006/flex/mx/internal::resultHandler()[E:\dev\gumbo_beta2\frameworks\projects\rpc\src\mx\rpc\AbstractInvoker.as:313]
at mx.rpc::Responder/result()[E:\dev\gumbo_beta2\frameworks\projects\rpc\src\mx\rpc\Responder.as:56]
at mx.rpc::AsyncRequest/acknowledge()[E:\dev\gumbo_beta2\frameworks\projects\rpc\src\mx\rpc\AsyncRequest.as:84]
at DirectHTTPMessageResponder/completeHandler()[E:\dev\gumbo_beta2\frameworks\projects\rpc\src\mx\messaging\channels\DirectHTTPChannel.as:446]
at flash.events::EventDispatcher/dispatchEventFunction()
at flash.events::EventDispatcher/dispatchEvent()
at flash.net::URLLoader/onComplete()

Strangely the update was working fine a couple of weeks ago. I looked at different forums and the common response is that the xml is invalid. However, I don't think my xml is invalid if it worked before. Here's what I have:

<fx:Declarations>
<mx:HTTPService id="student_requestsIndex" url="{CONTEXT_URL}/student_requests.xml"
                resultFormat = "e4x"
                result="student_requests=event.result as XML"/>

<mx:HTTPService id="student_requestsCreate" url="{CONTEXT_URL}/student_requests.xml"
                method = "POST"
                resultFormat="e4x"
                contentType="application/xml"
                result="student_requestsIndex.send()"/>

<mx:HTTPService id="student_requestsUpdate" url="{CONTEXT_URL}/student_requests/{student_requestsGrid.selectedItem.id}/confirm_request"
                method="POST"
                resultFormat = "e4x"
                contentType="application/xml" 
                headers="{{X_HTTP_METHOD_OVERRIDE: 'PUT'}}" />  
</fx:Declarations>

                            <mx:Form includeIn="Detail" x="-12" y="150" >

                            <mx:FormItem label="Student_num">
                                <s:TextInput id="student_numTextInput" text="@{student_requestsGrid.selectedItem.student_num}"/>
                            </mx:FormItem>
                        </mx:Form>
                        <s:Button includeIn="Detail" x="201" y="329"
                                  label="{student_requestsGrid.selectedItem.id==''?'Create':'Update'}" 
                                  click="student_requestsGrid.selectedItem.id=='' ? 
                                  student_requestsCreate.send(student_requestsGrid.selectedItem) :
                                  student_requestsUpdate.send(student_requestsGrid.selectedItem)"/>

The xml from Rails (note that confirm_request is actually an update action):

<student_requests>
<student_request>
<student_num>5</student_num>
<student_status>confirmed</student_status>
<updated_at>2010-03-02T21:49:43Z</updated_at>
</student_request>
<student_request>
<student_num>5</student_num>
<student_status>confirmed</stud开发者_StackOverflow社区ent_status>
<updated_at>2010-02-02T21:49:43Z</updated_at>
</student_request>
</student_requests>

Any suggestions? Thanks.