Error when trying to detect new updates for download

[FS-21]

Binary package hint: kpackagekit

When I click in "Details >>" I get this information:

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: kpackagekit 0.5.4-0ubuntu4
ProcVersionSignature: Ubuntu 2.6.32-21.32-generic 2.6.32.11+drm33.2
Uname: Linux 2.6.32-21-generic i686
NonfreeKernelModules: nvidia
Architecture: i386
Date: Fri May 7 01:35:40 2010
ProcEnviron:
 LANGUAGE=es_ES:es:en_GB:en
 LANG=es_ES.UTF-8
 SHELL=/bin/bash
SourcePackage: kpackagekit

[T L R (tlr)]

Thank you for taking the time to report this bug and helping to make Ubuntu better. This particular bug has already been reported and is a duplicate of bug #546607, so it is being marked as such. Please look at the other bug report to see if there is any missing information that you can provide, or to see if there is a workaround for the bug. Additionally, any further discussion regarding the bug should occur in the other report. Feel free to continue to report any other bugs you may find.