The glite-lb-client RPM is not installed by the glite-LB metapackage, although it IS installed by the glite-WMSLB metapackage.
Therefore, any sites running a stand-alone LB, when they apply the latest update, should manually download and install the glite-lb-client RPM from the gLite repository.
This package contains the glite-lb-purge.cron cron job used to make some cleanup in the MySQL database.