Internal system error.

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when i started my system ,a popup is showed on right bottom corner saying internal system error has occured ..wht does it means??
this detalis of error message ...
Error Type: <class 'yum.Errors.NoMoreMirrorsRepoError'&g t;
Error Value: failure: repodata/04da721e41b80b2a003de83f73387a6d7d30833f-primary.sqlite.bz2 from fedora: [Errno 256] No more mirrors to try.
File : /usr/share/PackageKit/helpers/yum/yumBackend.py, line 2202, in <module>
main()
File : /usr/share/PackageKit/helpers/yum/yumBackend.py, line 2199, in main
backend.dispatcher(sys.argv[1:])
File : /usr/lib/python2.5/site-packages/packagekit/backend.py, line 599, in dispatcher
self.dispatch_command(args[0], args[1:])
File : /usr/lib/python2.5/site-packages/packagekit/backend.py, line 503, in dispatch_command
self.get_distro_upgrades()
File : /usr/share/PackageKit/helpers/yum/yumBackend.py, line 1660, in get_distro_upgrades
pkgs = self.yumbase.pkgSack.returnNewestByName(name=&apos ;preupgrade&apos
File : /usr/lib/python2.5/site-packages/yum/__init__.py, line 592, in <lambda>
pkgSack = property(fget=lambda self: self._getSacks(),
File : /usr/lib/python2.5/site-packages/yum/__init__.py, line 435, in _getSacks
self.repos.populateSack(which=repos)
File : /usr/lib/python2.5/site-packages/yum/repos.py, line 251, in populateSack
sack.populate(repo, mdtype, callback, cacheonly)
File : /usr/lib/python2.5/site-packages/yum/yumRepo.py, line 168, in populate
db_fn = repo._retrieveMD(mydbtype)
File : /usr/lib/python2.5/site-packages/yum/yumRepo.py, line 1412, in _retrieveMD
cache=self.http_caching == 'all&apos
File : /usr/lib/python2.5/site-packages/yum/yumRepo.py, line 749, in _getFile
raise Errors.NoMoreMirrorsRepoError, errstr
wht do i do ??

[nimit]

somebody plz help me out ...wht is this error ??..