Openrasta Data Serialization Issue

I am currently using openRasta to build Rest Api.I am observing strange behavior while sending Ajax requests.Sometimes request is successful sometime it fails and it gives following exception.

{Exception:
System.Runtime.Serialization.SerializationException: Expecting element 'root' from namespace ''.. Encountered 'None'  with name '', namespace ''. 
   at System.Runtime.Serialization.Json.DataContractJsonSerializer.InternalReadObject(XmlReaderDelegator xmlReader, Boolean verifyObjectName)
   at System.Runtime.Serialization.XmlObjectSerializer.InternalReadObject(XmlReaderDelegator reader, Boolean verifyObjectName, DataContractResolver dataContractResolver)
   at System.Runtime.Serialization.XmlObjectSerializer.ReadObjectHandleExceptions(XmlReaderDelegator reader, Boolean verifyObjectName, DataContractResolver dataContractResolver)
   at System.Runtime.Serialization.Json.DataContractJsonSerializer.ReadObject(XmlDictionaryReader reader)
   at System.Runtime.Serialization.Json.DataContractJsonSerializer.ReadObject(Stream stream)
   at OpenRasta.Codecs.JsonDataContractCodec.ReadFrom(IHttpEntity request, IType destinationType, String paramName)
   at OpenRasta.OperationModel.Hydrators.RequestEntityReaderHydrator.TryReadPayloadAsObject(IHttpEntity requestEntity, IMediaTypeReader reader, IOperation operation)}

One thing i have observed is that when i keep browser idle for some time say more than 10 minutes i can see the request in firebug but it shows status as pending for long time and when it hits server it gives above exception.But same works fine sometimes.

Can anybody explain me this behavior?If want i can provide some additional code related to it.

Solution

The delay may just be caused by asp.net having to restart when you finally get out of idle, which takes a little while.

As for the error, it seems to be that the json data contract serializer can't parse the request. I'd advise to check a couple of things, and if it fails post here the details so we can help you further.

That the body is indeed correct at the time the error is triggererd (with fiddler)
That you do not have some asp.net-specific issues that would prevent the request from arriving correctly to the asp.net pipeline, such as cookies-based authentication or session management
That the request is not intercepted by any http module (anti forgery tokens etc).

Please provide your mappings, entities and a copy of the OR log (which you can get by attaching a debugger to the server process) and we'll try and help you further.