Thanks Chris & Mib

Was indeed fonts.

Reinstalled core Mavericks fonts and UI is back.

Had been cutting back fonts to all but core system mac and that caused problems.

Monaco Times and Lucida Grande were loaded so I suspect others.

Will detail more as I learn which fonts were responsible ...

Thanks - but unfortunately can't get to Prefs without UI.

Highly suspect of FontExplorerX font manager .
Will ditch it and reinstall core Mavericks fonts and let you know what happens.

Thanks - Peter

Fresh install

• 1.20 Demo
  XQuartz-2.7.5
  CUDA Driver Version: 5.5.28

User Interface text is invisible

Love this product - want to buy
Any thoughts?