It's a zip file, not a real Java JAR executable. You have to rename the .jar to .zip first and then you can open it with WinZip or whatever you use.
I was actually able to open it -
just didnt know what to do then
see the 2 attatched files* which I presume you've got to edit in somewhere or maybe place in some extensions folder somewhere ... along with all the other bits n pieces ..
*Had to rename files from .rdf
you're always a mine of info when it comes to FF
will try out all your suggestions
PS I'm sticking with the kid's
skin for the while (sounds a bit dodgy ??!) - all that grey needed an antidote !