Assertionerror at Zope startup after migrating to DirectoryStorage

Hi, my name is Fidel Leon, and I am an absolute Zope newbie...

I have upgrade one Zope instance from file to Directory Storage, just to see runzope throwing this:

----
2006-04-12T22:23:19 INFO(0) PlacelessTranslationService Applying patch
*** Patching ZPublisher.Publish with the get_request patch! ***
Traceback (most recent call last):
  File "/opt/Zope-2.7/lib/python/Zope/Startup/run.py", line 50, in ?
    run()
  File "/opt/Zope-2.7/lib/python/Zope/Startup/run.py", line 19, in run
    start_zope(opts.configroot)
  File "/opt/Zope-2.7/lib/python/Zope/Startup/__init__.py", line 51, in start_zope
    starter.startZope()
  File "/opt/Zope-2.7/lib/python/Zope/Startup/__init__.py", line 230, in startZope
    Zope.startup()
  File "/opt/Zope-2.7/lib/python/Zope/__init__.py", line 47, in startup
    _startup()
  File "/opt/Zope-2.7/lib/python/Zope/App/startup.py", line 57, in startup
    DB = configuration.dbtab.getDatabase('/', is_root=1)
  File "/opt/Zope-2.7/lib/python/DBTab/DBTab.py", line 96, in getDatabase
    db = self._createDatabase(name, is_root)
  File "/opt/Zope-2.7/lib/python/DBTab/DBTab.py", line 113, in _createDatabase
    db = factory.open()
  File "/opt/Zope-2.7/lib/python/Zope/Startup/datatypes.py", line 172, in open
    DB = self.createDB()
  File "/opt/Zope-2.7/lib/python/Zope/Startup/datatypes.py", line 169, in createDB
    return ZODBDatabase.open(self)
  File "/opt/Zope-2.7/lib/python/ZODB/config.py", line 97, in open
    return ZODB.DB(section.storage.open(),
  File "/opt/Zope-2.7/lib/python/DirectoryStorage/config.py", line 5, in open
    from DirectoryStorage.Storage import Storage
  File "/opt/Zope-2.7/lib/python/DirectoryStorage/Storage.py", line 1, in ?
    from Filesystem import Filesystem
  File "/opt/Zope-2.7/lib/python/DirectoryStorage/Filesystem.py", line 9, in ?
    from PosixFilesystem import PosixFilesystem as Filesystem
  File "/opt/Zope-2.7/lib/python/DirectoryStorage/PosixFilesystem.py", line 16, in ?
    from utils import ConfigParserError
  File "/opt/Zope-2.7/lib/python/DirectoryStorage/utils.py", line 77, in ?
    assert cPickle.dumps((('a','b'),None),1)=='((U\x01aU\x01btNt.'
AssertionError
----

My system is FC5 (Python 2.4.2), Zope 2.7.4 (this is a must), and Plone 2.0.5 (another must). Zope runs unders its own user/group (zope.zope), and I already have this in etc/zope.conf:
%import DirectoryStorage
<zodb_db main>
    # Main FileStorage database
        <directorystorage>
                path /opt/instancias/fidel/storage
                read-only off
        </directorystorage>
#    <filestorage>
#     path $INSTANCE/var/Data.fs
#    </filestorage>
    mount-point /
</zodb_db>

Any clue? I don't have a single idea about this :-(