I've had this error more than once. On a debian virtual machine, with Zend Core installed, and when mysql doesn't restart when the machine reboots. It looks something like this:

debian:/usr/local/Zend/mysql/bin# ./mysqld
080627 12:31:16 [ERROR] Can't find messagefile '/usr/local/mysql/share/mysql/english/errmsg.sys'
080627 12:31:16 [ERROR] Aborting

This is for two reasons. First: you need to be up one level of directory to be able to run these commands. Some errors will tell you that but this one doesn't. Secondly, you need to use the mysqld_safe command.

debian:/usr/local/Zend/mysql# bin/mysqld_safe
Starting mysqld daemon with databases from /usr/local/Zend/mysql/data

This works for me - I have no idea if it is the prescribed method but background the process above and you're good to go.