just to chime in....many of us here are perfectionists, I think, and this is NOT a small problem
However, I can say it's a setting in a file somewhere (duh
)...I had a hell of time getting Kompozer to show up in my Xfce menu....hell of a time finding the problem, easy fixing it...I use Kompozer for my business site, and launching from CLI would NOT do
Look around, compare other menu items icon settings, and see what's different. Just my .02. Thunar/Dolphin?/Konqueror are your friends
EDIT: sorry...everything in the Xfce menu exists in a .desktop (dot desktop) file.....check them out, compare...can't remember the directory right now....they all point to icons, where to execute the program from etc etc....sorry, mind is blank on the directory ....just search it....it's IN there and NOT (the icon referenced) somewhere else....
Find it and change it.