Publishing woes

I’ve been using RW for years now and every now and then I get a problem with publishing that I can’t understand - see image.
The problem is that I have changed nothing, apart from upgrading to RW 7. That’s it. Well apart from changing the pdf on a single page that is.
Does anyone have similar problems? If I carry pout the publishing ‘Test’ beforehand [it] tells me that everything is ok yet I still can’t publish and I’d like to know why.