It may also due to limit on DataContractSerializer with no. of items to serialize/deserialize
You can confirm this by turning on WCF logging with below entries:
<diagnostics>
<messageLogging logEntireMessage="true" logMalformedMessages="true" logMessagesAtTransportLevel="true" logMessagesAtServiceLevel="true" />
</diagnostics>
<system.diagnostics>
<sources>
<source name="System.ServiceModel" switchValue="All">
<listeners>
<add name="messages"
type="System.Diagnostics.XmlWriterTraceListener"
initializeData="c:\logs\messages.svclog" />
</listeners>
</source>
</sources>
</system.diagnostics>
If it's due to that limitation, you can increase the limit as given in this link:
http://social.msdn.microsoft.com/For...-5926b6cc527c/
All the best..
Siva Natarajan