soapUI unusable

Having previously used soapUI for 2 weeks succesfully, I now get an error on startup (screenshot attached) & am unable to perform any tasks including closing soapUI - get presented with the "Question" dialog box, but only the title bar is visible (i.e. no buttons) & can therefore can only close via Task Manager. Same issue occurs on attempting any task that results in a dialog box.

Have attempted to uninstall / reinstall & uninstall / manually delete all files / reinstall ... to no avail.