Plone 4.1 not start after Singing and Dancing 0.9.9 is uninstalled.

I have tried to uninstall S&D 0.9.9 from a plone 4.1 site.

Process:

deactive plugin in all plone sites
shutdown instance
comment out collective.singing and collective.dancing in buildout
run buildout (no errors)
start site

Error in all plone sites:

Site Error

An error was encountered while publishing this resource.

Sorry, a site error occurred.

Traceback (innermost last):

    Module ZPublisher.Publish, line 237, in publish_module_standard
    Module ZPublisher.Publish, line 179, in publish
    Module zope.event, line 23, in notify
    Module zope.component.event, line 24, in dispatch
    Module zope.component._api, line 136, in subscribers
    Module zope.component.registry, line 321, in subscribers
    Module zope.interface.adapter, line 583, in subscribers
    Module plone.transformchain.zpublisher, line 113, in applyTransformOnFailure
    Module plone.transformchain.zpublisher, line 79, in applyTransformOnSuccess
    Module plone.transformchain.zpublisher, line 55, in applyTransform
    Module zope.component._api, line 172, in queryUtility
    Module zope.component.registry, line 163, in queryUtility
    Module ZODB.Connection, line 860, in setstate
    Module ZODB.Connection, line 914, in _setstate
    Module ZODB.serialize, line 612, in setGhostState
    Module ZODB.serialize, line 605, in getState
    Module copy_reg, line 48, in _reconstructor

TypeError: ('object.__new__(Salt) is not safe, use Persistence.Persistent.__new__()', <function _reconstructor at 0x7f742a2e5c08>, (<class 'collective.dancing.channel.Salt'>, <type 'object'>, None))

Troubleshooting Suggestions

    The URL may be incorrect.
    The parameters passed to this resource may be incorrect.
    A resource that this resource relies on may be encountering an error.

For more detailed information about the error, please refer to the error log.

If the error persists please contact the site maintainer. Thank you for your patience.

Re-addding singing and dancing to site causes site to come back alive, but then it gets in the way of upgrade to plone 4.1.3

Please investigate

Instance information:
    Plone 4109

    CMF 2.2.4

    Zope 2.13.8

    Python 2.6.6 (r266:84292, Dec 26 2010, 22:31:48) [GCC 4.4.5]