function hideLoading(){
  	xajax.$('select_category').className = ''; 
  	xajax.$('select_category_value').className = ''; 
}
function showLoading(){
	xajax.$('select_category').className = 'loading'; 
	xajax.$('select_category_value').className = 'loading'; 
}  
//keep around the old call function
xajax.realCall = xajax.call;
//override the call function to bend to our wicked ways
xajax.call = function(sFunction, aArgs, sRequestType){
	showLoading();
	//call the old call function
	return this.realCall(sFunction, aArgs, sRequestType);
}