Cognos Trigger Problem

[PhilH]

We are trying to implement the scheduled generation of reports based on Cognos Trigger. We have a step within our SSIS package which fires the Trigger. The log file that we write to on firing tells us consistently that the Trigger fires successfully. However, the reports do not get produced each time.
We have multiple dispatchers. Having looked at the cogserver logs on each, the only message that I can find that corresponds with the time that the Trigger is being fired is:
"CNC-SDS-0222 An error occurred while trying to send a message in message manager."
This error appears on different dispatchers and the reports (when they run) appear to do so on different dispatchers only?
Has anyone had similar experiences or knows how best to proceed?