Remove the maintenance user ID alias relationship to the dbo master database owner before you add the master database as a replicate database.
2012/09/17 00:47:47 SQL Server message: msg 11105, level 11, state 1 2012/09/17 00:47:47 WARNING: "No such user/role 'xxxxxx' exists. "2012/09/17 00:47:47 Unable to execute query 'grant execute on rs_update_lastcommit to xxxxxx' against server 'xxxxxx'.The attempt to use rs_init to add the master database fails, because in the master database, the maintenance user ID is currently an alias of dbo. However, you cannot specify the maintenance user ID as the alias of dbo for the master database.
sp_dropalias loginame