MySQL Replication - Introduce new Slave to replication
Is this an issue with the fact now()
  is being in a query, which common
  sense tells me would cause issues if
  the inserts on that table were
  frequent enough??!?!


Yes, I believe this is the cause of your errors. Your method for introducing the new slave seems to be correct. It is quite strange in my opinion to define a table with a DATETIME field as the Primary Key. As you've quite rightly pointed out, the slave gets the replicated queries from the master and they will use the now() keyword in the queries, which will grab the timestamp from the local server.

Really, the table should be defined with some other data type for the PK (such as INT or BIGINT) which can be guaranteed to be unique, unlike a timestamp inserted with now().