--- a/Plugins/VcsPlugins/vcsMercurial/HgLogDialog.py	Fri Sep 02 07:57:13 2011 +0200
+++ b/Plugins/VcsPlugins/vcsMercurial/HgLogDialog.py	Fri Sep 02 08:21:31 2011 +0200
@@ -429,9 +429,8 @@
             return
         self.contents.scrollToAnchor(ver)
         
-        if self.diff:
-            del self.diff
-        self.diff = HgDiffDialog(self.vcs)
+        if self.diff is None:
+            self.diff = HgDiffDialog(self.vcs)
         self.diff.show()
         self.diff.start(filename, [v1, v2], self.bundle)