Constant font-lock-pre-idle-hook warnings from javascript mode

[bergbrains]

Hey, folks. I'm using XEmacs 21.4.21 and have been having consistent
problems using Karl Landstrom's javascript-mode.el. Every time I
change a JS file, I get the following warning:

(3) (warning/warning) Error caught in `font-lock-pre-idle-hook':
(error No match 1 in highlight (1 font-lock-keyword-face))

I sometimes get this in other modes as well, but not for some time.

I've been trying to find help via google, but to no avail. Anybody
out there nave any ideas how I can fix and/or squelch these errors.
Even if they came up in whatever frame *Warnings* was currently in
would be fine, but it insists on opening another window in the frame
in which the error occurs and showing the errors there. Very
disruptive.

Thanks for any light you may be able to shed on this.

Eric