Index: django/core/files/storage.py
===================================================================
--- django/core/files/storage.py	(revision 8448)
+++ django/core/files/storage.py	(working copy)
@@ -146,6 +146,10 @@
             try:
                 # This file has a file path that we can move.
                 if hasattr(content, 'temporary_file_path'):
+                    if os.name == 'nt':
+                        # If the temporary file is not closed on Windows, 
+                        # file_move_safe will fail.
+                        content.close()
                     file_move_safe(content.temporary_file_path(), full_path)
                     content.close()