Was trying to create a new group role today, in a group that I am Owner of. I was just activating all the permissions, as this was to be a new role/title for myself. About the 6th or 7th permissions box, I got an error that some XML was missing for a permission. Shortly after that, SL crashed.
When I got back in, I just made the role with no special permissions, as all it was for was to change the title over my head, anyway. Didn't stay to troubleshoot further, as I was on my lunch break and running out of time.
Still, someone needs to check and make sure the code for the role permissions is all working. It seems a couple of those are not.