Rated 5 out of 5 stars
Bardolfo and everybody else,
you can set Firefox to accept addons even if they are marked as not-compatible.
1) Open about:config
2) Right-click and select New -> Boolean
3) Enter this name:
If you're not using 3.6, adjust the number to your version.
4) Set it to false
Every time you update to a new version you have to recreate this setting with a new name to reflect the version change.
Now Fx should accept all add-ons. Even those which might crash the browser and maybe cause serious trouble. So use it wisely.