[Setup] Migration problem

[Hilde T Lauvset Rafaelsen]

Hi,
 
We run plone 2.5.3 on fedora 6 and want to upgrade to plone version 3.1.2 on
fedora 9.
 
I have installed Zope 2.10.5, python 2.4.5, plone 3.1.2 and have copied the
old database file from the old to the new server. Someone told me it was
best to upgrade to the newest stable release instead of upgrading in small
steps.
 
I have tried to follow the instruction given here :
 
http://plone.org/documentation/manual/upgrade-guide/version/2.5-3.0/updating
-2-5-3-to-3-0.3/migration-procedure 
 
When I try a portal_migration update I get this error message:

*	Starting the migration from version: 2.5.3-final 
*	Attempting to upgrade from: 2.5.3-final 
*	Set plone GS profile as default 
*	Upgrade to: 2.5.4-final, completed 
*	Attempting to upgrade from: 2.5.4-final 
*	Upgrade to: 2.5.4-2, completed 
*	Attempting to upgrade from: 2.5.4-2 
*	Upgrade to: 2.5.5, completed 
*	Attempting to upgrade from: 2.5.5 
*	Upgrade aborted 
*	Error type: zExceptions.BadRequest 
*	Error value: ('Empty or invalid id specified', '') 
*	File "/usr/lib/zope/lib/python/Products/CMFPlone/MigrationTool.py",
line 210, in upgrade newv, msgs = self._upgrade(newv) 
*	File "/usr/lib/zope/lib/python/Products/CMFPlone/MigrationTool.py",
line 321, in _upgrade res = function(self.aq_parent) 
*	File
"/usr/lib/zope/lib/python/Products/CMFPlone/migrations/v3_0/alphas.py", line
100, in three0_alpha1 migrateOldActions(portal, out) 
*	File
"/usr/lib/zope/lib/python/Products/CMFPlone/migrations/v3_0/alphas.py", line
446, in migrateOldActions new_category._setObject(action.id, new_action) 
*	File "/usr/lib/zope/lib/python/OFS/ObjectManager.py", line 314, in
_setObject v = self._checkId(id) 
*	File "/usr/lib/zope/lib/python/OFS/ObjectManager.py", line 81, in
checkValidId raise BadRequest, ('Empty or invalid id specified', id) 
*	End of upgrade path, migration has finished 
*	The upgrade path did NOT reach current version 
*	Migration has failed 

What thus this error message mean?????

Hilde