firefox gesture doesn't work

Why cant I use a gesture in firefox to go back one page? Under the Mozilla command 'back' and 'forward' are listed with left and right gestures programed but they do not work. Anyone?

Thanks.

PS
btw, the same commands work in internet explorer.

[url=http://tcbmi.com/strokeit/forum/read.php?f=2&i=848&t=762#reply_848]http://tcbmi.com/strokeit/forum/read.php?f=2&i=848&t=762#reply_848[/url]

Thanks so much!