Problem in importing contact data while using Infusionsoft server

To interact with an Infusionsoft Server, I wrote a spiffy XML-RPC interface to the Infusionsoft API. Everything was running quite well at the time of trial experiments. But when we imported contact data into the system through standard import people tool, the interface was throwing an exception to interact with one of these contacts. Literally the exception is mentioned below-
“2012-03-16 14:58:21,199 ERROR infusionsoft.ModelObserverBase: Caught exception in handleEvent()….. org.apache.xmlrpc.common.XmlRpcExtensionException: Null values aren't supported, if isEnabledForExtensions() == false” .
It is to inform that infusionsoft is the portion of the java class name of my interface, while handle event() is the method to catch the exception. The API method is the DataService.query, table=”contact”, being used to locate a contact using an id form my software system. But the execute() method on the RPC is throwing the exception. In this case I’ve two speculations; one is – the imported record is somehow missing some sort of important information, and the other is – as the interface is working efficiently without any imported contacts, so reasonably the exception can be thrown from the infusionsoft server, not from the client side. I’ve been directed to this site as the primary venue for this type of support. I would remain grateful to him/her who can help me to settle up this specific issue.
