PDFCreator seems to hold queue and then write PDFs in batches

We're running PDFCreator as a service on our printserver. It's currently running under the Domain Administrator account and it's shared to the clients over the network.

Printing PDFs works well but every now and then it seems to hold all print jobs and then jam them out all at the same time.

I get called a lot that printing PDFs doesnt work again and when I login to the printserver the whole queue suddenly goes through and when checking the PDF folder all the latest PDF's have the same Created/Mofied date.

Any ideas?