--- a/dulwich/object_store.py
+++ b/dulwich/object_store.py
@@ -22,6 +22,7 @@
 
 import itertools
 import os
+import shutil
 import stat
 import tempfile
 import urllib2
@@ -248,7 +249,12 @@
         basename = os.path.join(self.pack_dir, 
             "pack-%s" % iter_sha1(entry[0] for entry in entries))
         write_pack_index_v2(basename+".idx", entries, p.get_stored_checksum())
-        os.rename(path, basename + ".pack")
+        try:
+            os.rename(path, basename + ".pack")
+        except OSError:
+            # Hack for Windows access denied error.
+            # TODO: mark the original for deletion later.
+            shutil.copyfile(path, basename + ".pack")
         self._add_known_pack(basename)
 
     def add_thin_pack(self):

--- a/dulwich/pack.py
+++ b/dulwich/pack.py
@@ -128,7 +128,7 @@
 
 
 def load_pack_index(filename):
-    f = open(filename, 'r')
+    f = open(filename, 'rb')
     if f.read(4) == '\377tOc':
         version = struct.unpack(">L", f.read(4))[0]
         if version == 2:
@@ -181,7 +181,7 @@
         # ensure that it hasn't changed.
         self._size = os.path.getsize(filename)
         if file is None:
-            self._file = open(filename, 'r')
+            self._file = open(filename, 'rb')
         else:
             self._file = file
         self._contents, map_offset = simple_mmap(self._file, 0, self._size)
@@ -733,7 +733,7 @@
     :param objects: Iterable over (object, path) tuples to write
     :param num_objects: Number of objects to write
     """
-    f = open(filename + ".pack", 'w')
+    f = open(filename + ".pack", 'wb')
     try:
         entries, data_sum = write_pack_data(f, objects, num_objects)
     finally:
@@ -797,7 +797,7 @@
             crc32_checksum.
     :param pack_checksum: Checksum of the pack file.
     """
-    f = open(filename, 'w')
+    f = open(filename, 'wb')
     f = SHA1Writer(f)
     fan_out_table = defaultdict(lambda: 0)
     for (name, offset, entry_checksum) in entries:
@@ -945,7 +945,7 @@
             crc32_checksum.
     :param pack_checksum: Checksum of the pack file.
     """
-    f = open(filename, 'w')
+    f = open(filename, 'wb')
     f = SHA1Writer(f)
     f.write('\377tOc') # Magic!
     f.write(struct.pack(">L", 2))

--- a/dulwich/repo.py
+++ b/dulwich/repo.py
@@ -173,14 +173,12 @@
     def _get_ref(self, file):
         f = open(file, 'rb')
         try:
-            contents = f.read()
+            contents = f.read().strip()
             if contents.startswith(SYMREF):
                 ref = contents[len(SYMREF):]
-                if ref[-1] == '\n':
-                    ref = ref[:-1]
                 return self.ref(ref)
-            assert len(contents) == 41, 'Invalid ref in %s' % file
-            return contents[:-1]
+            assert len(contents) == 40, 'Invalid ref in %s' % file
+            return contents
         finally:
             f.close()