uninstall the old version
Install the new version from here
Sorry I can help you with this, I don't feel the need for this extension.
I've recently updated firefox (to 22.214.171.124) but my stumbleupon toolbar has vanished?
have looked in add ons in firefox tools and the info box says that this will be upgraded when firefox is restarted, but it doesn't
Also stumbleupon has vanished from my toolbar list (in view)
anyone feeling clever?