mysqld.sock path problem

/var/run/mysqld/mysqld.sock is the usual location of that socket. Every program that wants to connect to mysqld through socket will per default use that one. I dunno why you set mysql to place the socket to /tmp/mysqld.sock.

It's not my choice. Latest MySQL binary distribution ver. 4.1.12 uses /tmp/mysqld.sock as a default in all configuration files. Also in my old freeradius 1.0.2 installation also uses /tmp/mysqld.sock

What u could try is to set a symlink pointing to /tmp/mysqld.sock at /var/run/mysqld/mysqld.sock as workaround. I solved problem changing sock pid file path in /etc/my.cnf. I think the same must be configurable in freeradius.