Specifically, the warning is: (1) (warning/warning) Error caught in
`font-lock-pre-idle-hook': (invalid-function 0)

This is brand new behavior, upon updating ESS with Ubuntu's automatic
update, and downgrading to ESS version 5.4 resolves the behavior.

ESS version: 5.8-1karmic0   (downgrading to version 5.4 resolves behavior)
xemacs version: 21.4.22-ubuntu1
ubuntu version: 9.10 (jaunty)

	[[alternative HTML version deleted]]

