diff -r 63a1ee94b3ed Lib/importlib/_bootstrap.py
--- a/Lib/importlib/_bootstrap.py	Thu Oct 10 00:46:57 2013 -0700
+++ b/Lib/importlib/_bootstrap.py	Thu Oct 10 13:18:34 2013 +0200
@@ -24,6 +24,23 @@
 
 _CASE_INSENSITIVE_PLATFORMS = 'win', 'cygwin', 'darwin'
 
+_stat_cache = {}
+def _cached_stat(path):
+    cached = _stat_cache.get(path)
+    if cached is not None:
+        if isinstance(cached, OSError):
+            raise cached
+        else:
+            return cached
+
+    try:
+        stat = _os.stat(path)
+    except OSError as e:
+        _stat_cache[path] = e
+        raise
+    else:
+        _stat_cache[path] = stat
+    return stat
 
 def _make_relax_case():
     if sys.platform.startswith(_CASE_INSENSITIVE_PLATFORMS):
@@ -68,7 +85,7 @@
 def _path_is_mode_type(path, mode):
     """Test whether the path is the specified mode type."""
     try:
-        stat_info = _os.stat(path)
+        stat_info = _cached_stat(path)
     except OSError:
         return False
     return (stat_info.st_mode & 0o170000) == mode
@@ -456,7 +473,7 @@
 def _calc_mode(path):
     """Calculate the mode permissions for a bytecode file."""
     try:
-        mode = _os.stat(path).st_mode
+        mode = _cached_stat(path).st_mode
     except OSError:
         mode = 0o666
     # We always ensure write access so we can update cached files
@@ -878,7 +895,7 @@
         if filepath is None:
             return None
         try:
-            _os.stat(filepath)
+            _cached_stat(filepath)
         except OSError:
             return None
         for loader, suffixes in _get_supported_file_loaders():
@@ -1072,7 +1089,7 @@
 
     def path_stats(self, path):
         """Return the metadata for the path."""
-        st = _os.stat(path)
+        st = _cached_stat(path)
         return {'mtime': st.st_mtime, 'size': st.st_size}
 
     def _cache_bytecode(self, source_path, bytecode_path, data):
@@ -1390,7 +1407,7 @@
         is_namespace = False
         tail_module = fullname.rpartition('.')[2]
         try:
-            mtime = _os.stat(self.path).st_mtime
+            mtime = _cached_stat(self.path).st_mtime
         except OSError:
             mtime = -1
         if mtime != self._path_mtime: