Clicking on any of the check boxes corresponding to the languages listed under Edit -> Preferences -> Spell Checking, results in a bunch of check boxes getting (de-)selected. eg., if I clicked on English (Canada), then apart from English (Canada)'s check box, a number of different other check boxes also react.

However on re-visiting the menu, the state of the check boxes correctly represents result of your (de-)selection last time around. eg., even if your clicking on English (Canada) had wrongfully caused other buttons to react, on re-visiting the menu you will find that only English (Canada)'s state had changed and the other check boxes have not been affected.