Upgrading from breezy to dapper causes a Site Error with plone.

set up a plone site on breezy. (aptitude install plone plone-site)
Now upgrade zope-extendedpathindex to dapper, like so

Preparing to replace zope-extendedpathindex 2.1-2 (using .../zope-extendedpathindex_2.3-1_all.deb) ...
Unpacking replacement zope-extendedpathindex ...
Setting up zope-extendedpathindex (2.3-1) ...

Now observe as your website becomes like this:

Site Error

An error was encountered while publishing this resource.

AttributeError
Sorry, a site error occurred.

Traceback (innermost last):

    * Module ZPublisher.Publish, line 187, in publish_module_standard
    * Module Products.PlacelessTranslationService.PatchStringIO, line 51, in new_publish
    * Module ZPublisher.Publish, line 144, in publish
    * Module Zope2.App.startup, line 199, in zpublisher_exception_hook
    * Module ZPublisher.Publish, line 113, in publish
    * Module ZPublisher.mapply, line 88, in mapply
    * Module ZPublisher.Publish, line 40, in call_object
    * Module Shared.DC.Scripts.Bindings, line 311, in __call__
    * Module Shared.DC.Scripts.Bindings, line 329, in _bindAndExec
    * Module Shared.DC.Scripts.Bindings, line 348, in _bindAndExec
    * Module Products.CMFCore.FSPageTemplate, line 188, in _exec
    * Module Products.CMFCore.FSPageTemplate, line 127, in pt_render
    * Module Products.PageTemplates.PageTemplate, line 102, in pt_render
      <FSPageTemplate at /eyagi/document_view used for /eyagi/front-page>
    * Module TAL.TALInterpreter, line 202, in __call__
    * Module TAL.TALInterpreter, line 206, in __call__
    * Module TAL.TALInterpreter, line 250, in interpret
    * Module TAL.TALInterpreter, line 709, in do_useMacro
    * Module TAL.TALInterpreter, line 250, in interpret
    * Module TAL.TALInterpreter, line 426, in do_optTag_tal
    * Module TAL.TALInterpreter, line 411, in do_optTag
    * Module TAL.TALInterpreter, line 406, in no_tag
    * Module TAL.TALInterpreter, line 250, in interpret
    * Module TAL.TALInterpreter, line 709, in do_useMacro
    * Module TAL.TALInterpreter, line 250, in interpret
    * Module TAL.TALInterpreter, line 481, in do_setGlobal_tal
    * Module Products.PageTemplates.TALES, line 221, in evaluate
    * Module Products.PageTemplates.ZRPythonExpr, line 47, in __call__
      __traceback_info__: putils.createTopLevelTabs(actions)
    * Module Python expression "putils.createTopLevelTabs(actions)", line 1, in <expression>
    * Module Products.CMFPlone.PloneTool, line 734, in createTopLevelTabs
    * Module Products.LinguaPlone.patches, line 117, in searchResults
    * Module Products.CMFPlone.CatalogTool, line 458, in searchResults
    * Module Products.ZCatalog.ZCatalog, line 688, in searchResults
    * Module Products.ZCatalog.Catalog, line 734, in searchResults
    * Module Products.ZCatalog.Catalog, line 477, in search
    * Module Products.ExtendedPathIndex.ExtendedPathIndex, line 375, in _apply_index
    * Module Products.ExtendedPathIndex.ExtendedPathIndex, line 261, in search

AttributeError: _index_parents (Also, an error occurred while attempting to render the standard error message.)

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 error log.

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