All working now having changed my settings.
Strange thing is that I didn't conciously change the settings in the first place.
What's your operating system?
I'm tied to Windows, and I've found this sort of thing happening from time to time, but more frequently and in more applications with every new release of Windows, and especially right after an "upgrade". No idea what the mechanism is, and there seems to be no predicting what few things in what programs it will affect "this time", but it's happened enough times with parameters that I didn't even know existed that I know it's not simply my own carelessness. I've had to learn to roll with the punches, and to hunt for new parameters whenever something goes screwy.