I found what was causing the hangup for logout via IceWM's menu.
In the ~/.icewm/preferences file was a line (with comment) that said
Code:
# Command to start logout
LogoutCommand="logout"
Changing this to read:
Code:
# Command to start logout
LogoutCommand=""
made logout work again.
The change was not one I made myself. It was either introduced during experimenting with
the later version of IceWM, or else (more probably) put there by IceWM Control Panel, a utility
that, while useful in many ways, sometimes does unexpected things such as changing your
defaults in unpleasant fashion.
Case solved, though cause remains up in the air.