 				return;
 			
 			nasaService.changeStyleToMonth(style);
+		}
+		
+		private function verifyServiceName(s:String):Boolean
+		{
+			if (s == null || s == '')
+				return false;
+			
+			return WMSProviders.providers.indexOf(s) >= 0;
 		}
 	}
 }

				disposeObjects(_service);
			}
			
			// TEMPORARY SOLUTION
			// if there is no provider (which may happen due to ComboBox issue), default to NASA
			if (provider == '' || provider == null)
			{
				serviceName.delayCallbacks(); // prevent a recursive callback call for next line
				serviceName.value = WMSProviders.NASA;

		// the service and its parameters
		private var _service:IWMSService = null;
		public const preferLowerQuality:LinkableBoolean = registerNonSpatialProperty(new LinkableBoolean(false));
		public const serviceName:LinkableString = registerSpatialProperty(new LinkableString(WMSProviders.NASA, verifyServiceName), setProvider);
		public const srs:LinkableString = newSpatialProperty(LinkableString); // needed for linking MapTool settings
		public const styles:LinkableString = newNonSpatialProperty(LinkableString, setStyle); // needed for changing seasons
		public const displayMissingImage:LinkableBoolean = newNonSpatialProperty(LinkableBoolean);
