Duplicate binlog-do-db entry — Solution

At the November MySQL User Group, Patrick Galbraith ran into a problem where binlog-do-db was duplicated. It manifests itself like this:
(copied from http://lists.mysql.com/replication/607)

master my.cnf:
binlog-do-db=db1

slave my.cnf:
replicate-do-db=db1;

Relevant show slave status output

Replicate_Do_DB: db1;,db1;

When db1 is modified on master, Read_Master_Log_Pos and Relay_Log_Pos do
changes, also I can open and see the changes in rh3-relay-bin.000002, but
they do not appear in […]