Hi John,
mysql is trying to create a socket file on that path, but it cannot.
You have two different solutions:
1) create the path /usr/mnt.rom/card/mysql/tmp/ and make sure is writeable by the mysql user
2) at the mysql configuration file (check mysqlstart script to find out where that file is located), change the path of the mysql.sock file, so it is created in an exisiting path with proper write permissions
HTH