i have spent a week trying to connect my second computer to the first ispconfig with no success.
Then you have not setup your mysql server correctly on the master. Try:
mysql -h masterserver -u root -p
from the slave. This must work, if not, then you have not added the hostname of the master and slave server to the hosts files on both systems or the mysql of the amster server is not configured for root logins from the slave server.