Okay, I've figured out how to use the debugMode and the following probably answers my question: "Different sub-domain of chart .swf and dataURL. Both need to be same owing to sandbox security."
Here is my situation: I am running an application on Facebook. Facebook mediates all requests to my server through their pages. In other words, user requests go to Facebook, Facebook adds params and sends the request to me, I send the response back to Facebook, Facebook alters the response and presents it to the user.
So what happens is that the FusionChart SWF file thinks that the domain of the SWF is http://apps.facebook.com. So I can't tell it to load the XML data from somewhere like http://mainsocial.com/xmlData . I can tell it to load the XML data from somewhere like apps.facebook.com/myApp/xmlData, but Facebook returns errors because it doesn't know what to do with the returned XML.
Is there any way around this?