Well something else must be up... your code works in my setup perfectly, I can even add new keys and get their values... this is also on Dead Rat (Centos 5:).
Just to compare- I'm running memcached 1.2.2 compiled from source on x86_64, memcached user is "nobody" (not root).. my Cache::Memcached is version 1.24 from a CPAN install...
Comment on Re: Memcache 'get' returns undef running under mod_perl