Error An instance of PDFCreator is currently running

PDFCreator PDFCreator English
1

I hope someone can help.
I am working in c# with PDFCreator 4.2.0 and I keep getting the above error when trying to print multiple images.

I create my jobQueue as the code samples

private Queue CreateQueue()
{
// This needs to be done once to make the ComWrapper work reliably.
if (!_isTypeInitialized)
{
Type queueType = Type.GetTypeFromProgID("PDFCreator.JobQueue");
Activator.CreateInstance(queueType);
_isTypeInitialized = true;
}

        return new Queue();
    }

The application prints the first job then returns the error despite utilising jobQueue.ReleaseCom() after each print.
I understand you can utilise "IsInstanceRunning" but I am unable to find out how to do this.
Your help and possibly sample code would be much appreciated.

Regards
Stephen