You need to make sure the IP address of your other machine has permission to access the SQL server.
What you need to do is create a user with the host of your other machine, and set the permissions for that user. Once this is done you should be able to access MySQL on that box.
Cheers.
P.S. If you have a utility such as webmin, or phpMyAdmin this can be done very simply. Just go into "priveleges" and add new user.