The machine in question is running CentOS 5.7 and vsftpd-2.0.5-21.el5.x86_64.
My client can connect to the server and interact with it normally over standard FTP. It can also connect via FTPS and authenticate properly, but when my client (Filezilla) attempts a LIST command, it receives the following error;
GnuTLS error -53: Error in the push function
GnuTLS is fully updated from repo to gnutls-1.4.1-3.el5_4.8.x86_64.