... and just to confound us, it is now working again, without me doing anything I'm aware of.*
But now, per the screen shot, the colours are like an over-illuminated washed out pastel that makes it hard to distinguish between some materials. Any thoughts on that?
* I had to re-apply materials to the existing surfaces before the colours showed up outside of wire frame, so maybe the uninstall / reinstall worked but it was not evident until the materials were re-applied.