When forums are set to use separate groups, the students are not allowed into the discussion. I've only tested separate groups mode. I have the course mode set to separate and I have it forced. If I click Forums, the list of forums is not clickable for students. If I click the link to the forum from inside the course section it takes me to the discussion but I'm able to see the posts from other groups. If I click reply it gives an error that contains a link to an unknown language entry. Groups and forums seem completely broken.