Comment #13 on issue 99 by mrd000: Memcached 1.4.2 server segmentation fault http://code.google.com/p/memcached/issues/detail?id=99
Maybe dormando is right that the patch does not fix the main problem, it just helps to overcome it on affected configurations. The patch works for me, memcached works fine now under quite high load for several months. The server is on RedHat.
