Getting exceptions like object used after being disposed, NullReference while upload to Amazon.S3 - amazon-s3

Question

I have a code which reads file in stream and uploads it to amazon S3. I used Amazon .net SDK for Monotouch and Mono for Android which internally where Amazon SDK AssemblyVersion("1.5.2.1")
which is working fine.
But sometimes following exceptions are thrown while upload:
Message = The object was used after being disposed.;
StackTrace = at System.Net.WebConnection.BeginWrite (System.Net.HttpWebRequest request, System.Byte[] buffer, Int32 offset, Int32 size, System.AsyncCallback cb, System.Object state) [0x00000] in <filename unknown>:0
at System.Net.WebConnectionStream.BeginWrite (System.Byte[] buffer, Int32 offset, Int32 size, System.AsyncCallback cb, System.Object state) [0x00000] in <filename unknown>:0
Message = Object reference not set to an instance of an object;
StackTrace = at System.ServiceModel.Dispatcher.BaseMessagesFormatter.DeserializeReply (System.ServiceModel.Channels.Message message, System.Object[] parameters) [0x00000] in <filename unknown>:0
at System.ServiceModel.MonoInternal.ClientRuntimeChannel.Request (System.ServiceModel.Description.OperationDescription od, System.Object[] parameters) [0x00000] in <filename unknown>:0
at System.ServiceModel.MonoInternal.ClientRuntimeChannel.DoProcess (System.Reflection.MethodBase method, System.String operationName, System.Object[] parameters) [0x00000] in <filename unknown>:0
at System.ServiceModel.MonoInternal.ClientRuntimeChannel.Process (System.Reflection.MethodBase method, System.String operationName, System.Object[] parameters) [0x00000] in <filename unknown>:0
I've NOT set file stream = null or dispose for file stream being uploaded any where in code.
Found similar problem explained here
the line where I get exception, it tries to upload the given stream to s3.
More detailed explanation http://forums.xamarin.com/discussion/27098/getting-exceptions-like-object-used-after-being-disposed-nullreference-while-upload-to-amazon-s3
Some more stack traces:
--
UploadUsingHighLevelAPI; Message = Object reference not set to an instance of an object;
StackTrace = at System.Xml.XmlInputStream.Initialize (System.IO.Stream stream) [0x00000] in <filename unknown>:0
at System.Xml.XmlInputStream..ctor (System.IO.Stream stream) [0x00000] in <filename unknown>:0
at System.Xml.XmlStreamReader..ctor (System.IO.Stream input) [0x00000] in <filename unknown>:0
at System.Xml.XmlTextReader..ctor (System.IO.Stream input) [0x00000] in <filename unknown>:0
at Amazon.S3.AmazonS3Client.transform (System.String responseBody, System.String actionName, System.Type t) [0x00000] in <filename unknown>:0
at Amazon.S3.AmazonS3Client.processRequestError (System.String actionName, System.Net.HttpWebRequest request, System.Net.WebException we, System.Net.HttpWebResponse errorResponse, System.String requestAddr, System.Net.WebHeaderCollection& respHdrs, System.Type t, System.Exception& cause) [0x00000] in <filename unknown>:0
at Amazon.S3.AmazonS3Client.handleHttpWebErrorResponse (Amazon.S3.Model.S3Request userRequest, System.Net.WebException we, System.Net.HttpWebRequest request, System.Net.HttpWebResponse httpResponse, System.Exception& cause, System.Net.HttpStatusCode& statusCode) [0x00000] in <filename unknown>:0
at Amazon.S3.AmazonS3Client.getResponseCallback[PutObjectResponse] (IAsyncResult result) [0x00000] in <filename unknown>:0
--
UploadUsingHighLevelAPI; Message = Error: SendFailure (Error writing headers);
StackTrace = at System.Net.HttpWebRequest.EndGetRequestStream (IAsyncResult asyncResult) [0x00000] in <filename unknown>:0
at System.Net.HttpWebRequest.GetRequestStream () [0x00000] in <filename unknown>:0
at Amazon.S3.AmazonS3Client.getRequestStreamCallback[PutObjectResponse] (IAsyncResult result) [0x00000] in <filename unknown>:0