I was able to figure out what I think was going on for you. The current patch (1.6.5) should solve it (I am thinking there was an attack missed flag that wasn't being cleared on a bunch of your characters making it so status effects couldn't be applied). If it is not fixed, please email me your save (email is in the ChangeLog) so I can take a look at it.
And yeah, if you ever run into anything that is broken in a current version that wasn't in a previous, you can always roll back and the issue should fix itself in most cases. In the case of your issue, it was something that would have started on 1.6.4.