I have copied a .ctwmrc found on the internet, and with that my ability to use function-keys F1 to F12, apart from F9 has been restored. So the bug was in some recent change to my large and messy .ctwmrc. I am gradually copying things from the old file into the new one and checking what does and does not work. A slow process. But I should eventually learn what was wrong with my old .ctwmrc.
Apologies for blaming this on a change in ctwm! Aaron http://www.cs.bham.ac.uk/~axs
