--- a/lib/js/urweb.js	Tue Sep 22 13:27:47 2009 -0400
+++ b/lib/js/urweb.js	Tue Sep 22 13:41:23 2009 -0400
@@ -883,7 +883,7 @@
         stack = cons({c: "a3", env: env}, stack.next);
         break;
       default:
-        throw "Unknown Ur continuation kind";
+        throw ("Unknown Ur continuation kind " + fr.c);
       }
 
       break;
@@ -922,7 +922,7 @@
         throw "Empty Ur record in interpretation";
       var fs = {};
       stack = cons({c: "r", n: e.l.data.n, fs: fs, l: e.l.next}, stack);
-      e = e.l.data;
+      e = e.l.data.v;
       break;
     case ".":
       stack = cons({c: ".", f: e.f}, stack);
@@ -942,7 +942,7 @@
       e = {c: "c", v: cs(function() { return exec0(env0, e0); })};
       break;
     default:
-      throw "Unknown Ur expression kind";
+      throw ("Unknown Ur expression kind " + e.c);
     }
   }
 }