packagekit error when get updates from repo's offline

[Marco]

Binary package hint: packagekit

Having installed Medibuntu directory, I now find that I get the following message when attempting to get updates:

Could not download all repository indexes

The repository may no longer be available or could not be contacted because of network problems. If available an older version of the failed index will be used. Otherwise the repository will be ignored. Check your network connection and ensure the repository address in the preferences is correct.

This problem isn't managed well by packagekit and kpackagekit report this:

Error Type:
Error Value: coercing to Unicode: need string or buffer, exceptions.SystemError found
File : /usr/share/PackageKit/helpers/apt/aptBackend.py, line 2216, in
main()
File : /usr/share/PackageKit/helpers/apt/aptBackend.py, line 2213, in main
run(args, options.single)
File : /usr/share/PackageKit/helpers/apt/aptBackend.py, line 2175, in run
backend.dispatcher(args)
File : /usr/lib/python2.6/dist-packages/packagekit/backend.py, line 699, in dispatcher
self.dispatch_command(args[0], args[1:])
File : /usr/lib/python2.6/dist-packages/packagekit/backend.py, line 606, in dispatch_command
self.refresh_cache(force)
File : /usr/share/PackageKit/helpers/apt/aptBackend.py, line 202, in _locked_cache
func(*args, **kwargs)
File : /usr/share/PackageKit/helpers/apt/aptBackend.py, line 1498, in refresh_cache
format_string(error.message))
File : /usr/lib/python2.6/dist-packages/packagekit/backend.py, line 723, in format_string
txt = unicode(text, encoding, errors='replace')

ProblemType: Bug
DistroRelease: Ubuntu 10.04
Package: packagekit 0.5.7-0ubuntu2 [modified: var/lib/PackageKit/transactions.db]
ProcVersionSignature: Ubuntu 2.6.32-21.32-generic 2.6.32.11+drm33.2
Uname: Linux 2.6.32-21-generic x86_64
NonfreeKernelModules: nvidia
Architecture: amd64
CheckboxSubmission: 88a98775d78448f97638aa764302e1cc
CheckboxSystem: ed86e29ffba809c116a39e33fa9fc45c
Date: Mon Apr 19 09:23:48 2010
ProcEnviron:
 LANGUAGE=it_IT:it:en_GB:en
 LANG=it_IT.UTF-8
 SHELL=/bin/bash
SourcePackage: packagekit