diff --git a/direct/src/plugin/p3dMultifileReader.cxx b/direct/src/plugin/p3dMultifileReader.cxx
index 5b9eef39ea..e96ce50f00 100644
--- a/direct/src/plugin/p3dMultifileReader.cxx
+++ b/direct/src/plugin/p3dMultifileReader.cxx
@@ -208,6 +208,11 @@ read_index() {
     s._start = read_uint32();
     s._length = read_uint32();
     unsigned int flags = read_uint16();
+    if ((flags & 0x18) != 0) {
+      // Skip over the uncompressed length.
+      read_uint32();
+    }
+      
     s._timestamp = read_uint32();
     size_t name_length = read_uint16();
     char *buffer = new char[name_length];
diff --git a/direct/src/plugin/p3dSession.cxx b/direct/src/plugin/p3dSession.cxx
index 9692686ade..79115310ad 100644
--- a/direct/src/plugin/p3dSession.cxx
+++ b/direct/src/plugin/p3dSession.cxx
@@ -702,7 +702,7 @@ start_p3dpython(P3DInstance *inst) {
   const char *keep[] = {
     "TMP", "TEMP", "HOME", "USER", 
 #ifdef _WIN32
-    "SYSTEMROOT", "USERPROFILE",
+    "SYSTEMROOT", "USERPROFILE", "COMSPEC",
 #endif
     NULL
   };
diff --git a/direct/src/showbase/VFSImporter.py b/direct/src/showbase/VFSImporter.py
index 026212be26..f19f7e00ea 100644
--- a/direct/src/showbase/VFSImporter.py
+++ b/direct/src/showbase/VFSImporter.py
@@ -8,7 +8,7 @@ import imp
 import struct
 import __builtin__
 
-__all__ = ['register']
+__all__ = ['register', 'reload_from', 'reload_packages']
 
 vfs = VirtualFileSystem.getGlobalPtr()
 
@@ -274,3 +274,43 @@ def register():
         _registered = True
         sys.path_hooks.insert(0, VFSImporter)
     
+def reload_from(root_path, moduleName):
+    """ Reloads the named module from the indicated root directory,
+    merging it with the module already loaded, if any.  This is
+    particularly useful for merging a VFS-mounted package with a
+    previously-frozen package.  It allows you to release the initial
+    version of a package via the freeze mechanism, while still
+    allowing new additions to be added later via multifile.
+
+    See also reload_packages(), which is a convenience function
+    wrapped around this one.  """
+
+    path = root_path + '/' + '/'.join(moduleName.split('.')[:-1])
+    importer = VFSImporter(path)
+    loader = importer.find_module(moduleName)
+    if loader:
+        loader.load_module(moduleName)
+        
+def reload_packages(multifile, root_path):
+    """ Walks the multifile and looks for Python packages that already
+    exist as frozen modules.  For any such packages found, calls
+    reload_from() to merge them with the preloaded frozen package. """
+
+    for i in range(multifile.getNumSubfiles()):
+        filename = multifile.getSubfileName(i)
+        isInit = False
+        for ext in ['py'] + compiledExtensions:
+            if filename.endswith('/__init__.' + ext):
+                isInit = True
+                break
+        if not isInit:
+            continue
+
+        # Found a package.
+        moduleName = '.'.join(filename.split('/')[:-1])
+        module = sys.modules.get(moduleName, None)
+        if module:
+            file = getattr(module, '__file__', None)
+            if file == '<frozen>':
+                # It's a frozen module; replace it.
+                reload_from(root_path, moduleName)
diff --git a/direct/src/showutil/FreezeTool.py b/direct/src/showutil/FreezeTool.py
index 315cc2a3e1..dd7fb9d6ca 100644
--- a/direct/src/showutil/FreezeTool.py
+++ b/direct/src/showutil/FreezeTool.py
@@ -720,7 +720,7 @@ class Freezer:
         for mdef in autoIncludes:
             try:
                 self.__loadModule(mdef)
-                # Since it succesfully loaded, it's no longer a guess.
+                # Since it successfully loaded, it's no longer a guess.
                 mdef.guess = False
             except:
                 # Something went wrong, guess it's not an importable
diff --git a/direct/src/showutil/packp3d.py b/direct/src/showutil/packp3d.py
index b12aa3fbaf..faaa2ecce9 100755
--- a/direct/src/showutil/packp3d.py
+++ b/direct/src/showutil/packp3d.py
@@ -132,7 +132,13 @@ def main(appRunner):
     """ This function is called when this module is invoked as
     packp3d.p3d. """
 
-    makePackedApp(appRunner.argv[1:])
+    print "args = %s" % (appRunner.argv,)
+    try:
+        makePackedApp(appRunner.argv[1:])
+    except ArgumentError, e:
+        print e.args[0]
+        sys.exit(1)
+    sys.exit(0)
 
 if __name__ == '__main__':
     try:
diff --git a/direct/src/showutil/runp3d.py b/direct/src/showutil/runp3d.py
index 83b5b42518..ecfa88c1a3 100755
--- a/direct/src/showutil/runp3d.py
+++ b/direct/src/showutil/runp3d.py
@@ -300,6 +300,7 @@ class AppRunner(DirectObject):
 
         # Mount the Multifile under /mf, by convention.
         vfs.mount(mf, MultifileRoot, vfs.MFReadOnly)
+        VFSImporter.reload_packages(mf, MultifileRoot)
 
         # Load any prc files in the root.  We have to load them
         # explicitly, since the ConfigPageManager can't directly look