rubygems error

After this operation, 0B of additional disk space will be used.
Setting up rubygems1.8 (1.3.7-1ubxd2) ...
update-alternatives: error: alternative gem can't be master: it is a slave of ruby
dpkg: error processing rubygems1.8 (--configure):
 subprocess installed post-installation script returned error exit status 2
dpkg: dependency problems prevent configuration of rubygems:
 rubygems depends on rubygems1.8 (= 1.3.7-1ubxd2); however:
  Package rubygems1.8 is not configured yet.
dpkg: error processing rubygems (--configure):
 dependency problems - leaving unconfigured
No apport report written because the error message indicates its a followup error from a previous failure.
                                                                                                          Errors were encountered while processing:
 rubygems1.8
 rubygems
E: Sub-process /usr/bin/dpkg returned an error code (1)