my kpackagekit doesn't work when i refresh it
 

first hello my name is Giovanni im new to Linux and my problem is that my kpackagekit doesn't work.I open it then I check to see if there are any upgrades it needs there aren't any so I refresh it.the next thing that happens is that it gives me an error message.I get this an internal error has occurred.Then there's 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')I don't know what to do so if someone could help me please I would appreciate it

What is the output of
in the terminal?

thanks