auto-cap. And problems with lookup-key under xemacs-21.1.14

Hello I am aware that this is a little off topic, but I could not find a answer in the comp.emacs.xemacs newsgroup, I also think that this error is still present in 21.4, which I only tried briefly. Auto-capitalize is a very nifty minor mode which as it names says capitalize words for you. It is written for GNU emacs and under xemacs the following problem occurs when using the mouse. The problem is that lookup-key signals an error when it's passed a misc-user-event KEY, which apparently corresponds to a menu or toolbar click. I attach the error message below. So the consequence is that one cannot use the mouse decently while auto-capitalize is on. The author thinks this is a BUG of Xemacs, since there is no similar problem under GNU emacs. Anybody has an idea Thanks Uwe Brauer ERROR