diff --git a/chrome/content/zotero/overlay.js b/chrome/content/zotero/overlay.js
index d1029baf2..66f520752 100644
--- a/chrome/content/zotero/overlay.js
+++ b/chrome/content/zotero/overlay.js
@@ -838,6 +838,11 @@ var ZoteroPane = new function()
 		if (this.itemsView)
 		{
 			this.itemsView.unregister();
+			document.getElementById('zotero-items-tree').removeEventListener(
+				'keypress', this.itemsView.wrappedJSObject.listener, false
+			);
+			this.itemsView.wrappedJSObject.listener = null;
+			document.getElementById('zotero-items-tree').view = this.itemsView = null;
 		}
 		
 		document.getElementById('zotero-tb-search').value = ""; 
diff --git a/chrome/content/zotero/xpcom/itemTreeView.js b/chrome/content/zotero/xpcom/itemTreeView.js
index a9690dc8f..7b7efdbbd 100644
--- a/chrome/content/zotero/xpcom/itemTreeView.js
+++ b/chrome/content/zotero/xpcom/itemTreeView.js
@@ -112,7 +112,7 @@ Zotero.ItemTreeView.prototype.setTree = function(treebox)
 		var expandAllRows = obj.expandAllRows;
 		var collapseAllRows = obj.collapseAllRows;
 		var tree = obj._treebox.treeBody.parentNode;
-		tree.addEventListener('keypress', function(event) {
+		var listener = function(event) {
 			var key = String.fromCharCode(event.which);
 			
 			if (key == '+' && !(event.ctrlKey || event.altKey || event.metaKey)) {
@@ -124,7 +124,11 @@ Zotero.ItemTreeView.prototype.setTree = function(treebox)
 				obj.collapseAllRows(treebox);
 				return;
 			}
-		}, false);
+		};
+		// Store listener so we can call removeEventListener()
+		// in overlay.js::onCollectionSelected()
+		obj.listener = listener;
+		tree.addEventListener('keypress', listener, false);
 		
 		obj.sort();
 		obj.expandMatchParents();
@@ -774,6 +778,10 @@ Zotero.ItemTreeView.prototype.toggleOpenState = function(row, skipItemMapRefresh
 		}
 	}
 	
+	if (!count) {
+		return;
+	}
+	
 	this._dataItems[row].isOpen = !this._dataItems[row].isOpen;
 	this._treebox.rowCountChanged(row+1, count); //tell treebox to repaint these
 	this._treebox.invalidateRow(row);