Java :: Handling Custom Exceptions With Throwable Cause In Flex

I am using a custom java exception to provide the flex client with more info than the exception itself. My exception extends Exception and it has a attribute with the needed info for the client. Well, my problem is the following: when I build my exception if I invoke super() or super("message") the flex client can access all the info properly. But if I build the exception with a Throwable cause, super(cause), then the flex client can only access to stackTrace.

public class MyException extends Exception {
private String errorCode;
public String getErrorCode() {
return errorCode;
} public void setErrorCode(String errorCode) {
[Code] ......

By using MyException(String msg) the flex client can access to errorCode
By using MyException(Throwable cause) the flex client can't access to errorCode

In the flex side the code is:
var faultEvent : FaultEvent = FaultEvent( event );
var errorMessage:ErrorMessage = faultEvent.message as ErrorMessage;
var codeError:String = errorMessage.rootCause.errorCode;