FYI I want to share this with others JIC you didn't know. I asked a question about slave compatibility between masters and slaves of different versions. Here is the compatibility matrix chart found. http://www.mysql.com/doc/en/Replication_Implementation.html
Master Master Master Master 3.23.33 and up 4.0.0 4.0.1 4.0.3 and up Slave 3.23.33 and up yes no no no Slave 4.0.0 no yes no no Slave 4.0.1 yes no yes no Slave 4.0.3 and up yes no no yes - Dathan Vance Pattishall - Sr. Programmer and mySQL DBA for FriendFinder Inc. - http://friendfinder.com/go/p40688