Just click it. It told me to come here and post this bug!
What the hell, i've seen something similar with the "illegal usernames'' but never something like this. Im really curious how this happened.
I think it is just cause that thread got closed. I just tried it on another user in that thread and I got the same page.
Try it again now. h3r3tic was right, it's the error from trying to assign APs to a closed thread. I've inserted a more relevant error message.
I'm not mean. You're just a sissy.