Recently hard killed xfce4 & kde processes running, and since then, gtk1 apps (eg qjackctl & madman) now use the the ugly default theme.
Also, "switch" (gtk-theme-switch) fails to preview the alternative themes - selecting each theme in turn and previewing it shows the same (default) theme.
gtk2 themes (and switch2) are fine.
Can someone identify what I might have corrupted and recommend a solution.
Edit: My stupidity (yes there are stupid questions in Newbie Corner ) - It was a qt problem. Solved by running qtconfig and changing GUI theme from "unknown" to "polyester".