I too use Comodo and have a minor issue with it.  Whenever I update Qimage it insists on Print to File unless I disable Sandbox and keep it disabled ie it won't allow using the printer.  I'm trying to remember the error messages/prompts I used to receive.  Might be worth checking.  If that turns out to be the issue and you want to keep sandbox enabled I'll check what I did to allow that (I don't enable sandbox currently).

Good luck

Sandy