Rated 1 out of 5 stars

by DutchGlory on Oct. 12, 2013 ·

does not work with FF v.25

This review is for a previous version of the add-on (7.0.1). 

by jooliaan (Developer) on Oct. 12, 2013 ·

I'm using United States English Spellchecker together with Firefox 25 beta 7 and it works properly.
Try it by creating a new clean Firefox profile.