Did you try just with
without the version number? Or with "force" switch,
Code:
rpm --force -e gpar2
would it help? It's also possible that the package is broken, that the script which is to be run after the actual removal process, is somehow messed up and can't be run, in which case the package itself might not be removed the usual way. In this case you'd need to either fix the post-rm script, if that's the problem, or just find another way to force rpm to remove the package's files.