Tried all the C++/DirectX reinstalling, even goiung so far as wiping the game complete and reinstalling and sitting through the painfully slow updates again. Played fine for about three hours, then, of course, back to the runtime error. Again, not location specific I don't think, or indeed area population - I wast going through Western Thanalan, which is usually quite busy, but was remarkably quiet as I think most people are off into the higher level areas just now. Anyway here's hoping this gets resolved/recognised soon - it's becoming too regular for comfort.