Comment 7 for bug 539190

Ashley,

percona-xtradb is superseded by percona-server now. See http://www.mysqlperformanceblog.com/2010/06/21/percona-server-5-1-47-rel11-0/ for more details.

You have to install percona-server-client-5.1 instead.
Don't get confused by -server part. "Percona Server" is the product name, while -client, -common, -server are the suffixes of the respective sub-packages.