diff -r c48d069163d6 -r b18ce742566a mercurial/mdiff.py
--- a/mercurial/mdiff.py	Sun Jun 12 08:51:11 2005 -0800
+++ b/mercurial/mdiff.py	Sun Jun 12 10:18:32 2005 -0800
@@ -67,7 +67,11 @@
     for i in a: p.append(p[-1] + len(i))
 
     if sorted:
-        d = sortdiff(a, b)
+        try:
+            d = sortdiff(a, b)
+        except:
+            print a, b
+            raise
     else:
         d = difflib.SequenceMatcher(None, a, b).get_matching_blocks()
     la = 0