So I come across an issue where I had to reset replication master in MySQL 5.1 (but it is the same I believe in later 5.X versions as well)
There is great blog here and below is the core of the steps needed:
Login on the slave as administrator
STOP SLAVE;
RESET SLAVE;
CHANGE MASTER TO MASTER_HOST="master_name_or_address", MASTER_USER="administrator_username", MASTER_PASSWORD="administrator_password", MASTER_LOG_FILE="logfile_from_master", MASTER_LOG_POS=position_from_master;
START SLAVE;
and a bit later verify using
SHOW SLAVE STATUS\G
To get the position and filename for the CHANGE MASTER command use the followin on the master server:
SHOW MASTER STATUS;
Any more details see the blog mentioned earlier.
Cheers