Comment 10 for bug 1007164

The official guide (http://dev.mysql.com/doc/refman/5.5/en/creating-ssl-certs.html) has -set_serial 01 for both server and client certificates, that is the reason why the issue appears.

use -set_serial 02 for the client certificate, and everything should be good. Make sure the output of the check command is the same as in the howto (openssl verify ...).