Problem with Nego!

Dear all, I hope anyone can help me. I cannot create any longer pdf files with Nego (billing programme), before it was not a problem at all, it comes all of a sudden and even my classic printer does not work any longer with Nego (message received: "No default printer installed"). This problem seems not to be due do Nego. Otherwise pdf creator works fine. Thanks for your help, I'm really desperate, cannot invoice any longer !!!