This patch adds functionality to destroy the dialog to cleanup memory. 
Index: dojo-release-1.3.2-src/dijit/Dialog.js
===================================================================
--- dojo-release-1.3.2-src.orig/dijit/Dialog.js	2009-09-04 11:21:13.000000000 -0700
+++ dojo-release-1.3.2-src/dijit/Dialog.js	2009-09-04 11:22:00.000000000 -0700
@@ -120,6 +120,7 @@
 			this.connect(this, "onExecute", "hide");
 			this.connect(this, "onCancel", "hide");
 			this._modalconnects = [];
+			this._subscriptions = [];
 		},
 
 		onLoad: function(){
@@ -165,7 +166,7 @@
 				this._moveable = (dojo.isIE == 6) ?
 					new dojo.dnd.TimedMoveable(node, { handle: this.titleBar }) :	// prevent overload, see #5285
 					new dojo.dnd.Moveable(node, { handle: this.titleBar, timeout: 0 });
-				dojo.subscribe("/dnd/move/stop",this,"_endDrag");
+				this._subscriptions.push(dojo.subscribe("/dnd/move/stop",this,"_endDrag"));
 			}else{
 				dojo.addClass(node,"dijitDialogFixed"); 
 			}
@@ -403,9 +404,22 @@
 				this._position();
 			}
 		},
-		
+
+		// destroy and remove the DOM elements on close instead of just hiding
+		close: function() {
+			// wait for the fadeOut ends before destroy. invoking hide() cause fadeOut to play
+			this.connect(this._fadeOut, "onEnd", function() {
+				this.destroy();
+			});
+			this.refocus = false;
+			this.hide();
+		},
+
 		destroy: function(){
+			delete this._fadeIn;
+			delete this._fadeOut;
 			dojo.forEach(this._modalconnects, dojo.disconnect);
+			dojo.forEach(this._subscriptions, dojo.unsubscribe);
 			if(this.refocus && this.open){
 				setTimeout(dojo.hitch(dijit,"focus",this._savedFocus), 25);
 			}