Rated 5 out of 5 stars

Manual fix for version 1.3.2:
Changing line 49 of content/browser.js (dictionary-switcher.jar) to
var spellchecker = Components.classes[spellclass].getService(Components.interfaces.mozISpellCheckingEngine);
seems to fix the problem.

Would be nice to see an official version 1.3.3 soon :-)

This review is for a previous version of the add-on (1.3.2.1-signed.1-signed).  This user has a previous review of this add-on.