They are plenty ways to display the fault event.  Here are some different ways to display your error in Flex 3. The first one seems to be the most complete for me, it returns where the error occured and the reason why if failed. 

private function fault(evt:FaultEvent):void {

 

    Alert.show(evt.fault.faultString, evt.fault.faultCode);              

}

Another way to display the error message is to use the FaultString as the title and the FaultDetail as the message.

private function fault(evt:FaultEvent):void {

    Alert.show(evt.fault.faultString, evt.fault.faultDetail);                

}

This example displays all the error messages in a jumbled mess within the alertbox, but some people might like it.

private function fault(evt:FaultEvent):void {

    Alert.show(evt.fault.message);               

}