Can't reply to Group Posts

Firstly.. there seems to be a new problem that has started since the upgrade yesterday. I've noticed other people have had to create new threads in groups because they are unable to reply to posts in Groups. When replying it ends up at the 404 error page.

Also, in reply to the post about allowing a couple of sample lessons per level for people to see if they want to subscribe to cPOD. The free 7 day trial provides Premium level access to the site for all lessons and premium content.