Index: trunk/web-app/js/overlayPane.js
===================================================================
--- trunk/web-app/js/overlayPane.js	(revision 307)
+++ trunk/web-app/js/overlayPane.js	(revision 309)
@@ -8,7 +8,4 @@
 
 function hideAssetTreePane(paneDivId, tableDivId, saveUrl) {
-
-    // Hide the pane.
-    $(paneDivId).toggle();
 
     var visibleDivs = $(tableDivId).select('div').findAll(function(el) { return el.visible(); })
@@ -25,5 +22,9 @@
 
     // Post the id's of all visible divs.
-    new Ajax.Request(saveUrl, {parameters: params});
+    // asynchronous: false is against the prototype recommendations but appears to be needed in this case.
+    new Ajax.Request(saveUrl, {parameters: params, asynchronous: false});
+
+    // Hide the pane.
+    $(paneDivId).toggle();
 }