GNU tar. gnome-control-center relies on the tar/gzip/bzip2 *binaries* to extract themes. Subsequently it can't tell if things go wrong. This is one very good reason why fixing the tar/gz/bz2 vfs methods would be a very good thing.
2003-06-03 Andrew Sobala <aes@gnome.org> * themus-properties-view.c: fix description word wrapping * theme-method.c: gcc 2.x compile
The grand "themus->control-center" merge. See individual ChangeLogs for details.