SQL Server 2008 - Replication - Add Articles - Error clicking on Start on Snapshot Agent Status - Error 20678

Adding new articles (new tables) to replicate.

This is the process I followed which worked the last time I used it.

•Publisher (REPL_ISIS_APPS) --> Properties
•Articles page
•Click off ‘Show only checked articles in the list’
•Click on extra tables to add
•Click on OK
•Publisher (REPL_ISIS_APPS) --> View Snapshot Agent Status
•On View Snapshot Agent Status page click on Start

On the last step an error message is displayed.

Error message reads :-
BEGIN
The Agent could not be started

An exception occurred while executing a transaction-SQL statement or batch.
(Microsoft.SqlServer.ConnectionInfo)

Could not find regular snapshot job for specified publication 'REPL_ISIS_APPS'.
Supply either @job_id or @job_name to identify the job.
Changed database context to 'ISIS'. (Microsoft SQL Server, Error 20678)
END

Q1) Does anyone know what caused this error?
Q2) Is there anyway to fix this error?
Q3) Would the option 'Reinitialize All Subscriptions' (with Use a new snapshot and generate the new snapshot now) correct this issue or make the issue worse?

At present all tables replicate (except the new ones I want to replicate) fine. What I don't want is to be in a situation where things stop replicating all together.

I have tried searching the internet for resolutions to this but I cannot seem to find this exact scenario.

Can you help?

Regards,
Richard.