On the friends list, a group was suddenly moved to the very bottom.

As the title says, in the client, on my friends list, I have a group specifically for a certain group of people. Normally, I have them at the very top of the list, above the default general group. However, now when I log in, they're at the very bottom, and they're locked there. When I try to move the group up or down, it doesn't move.

How do I fix this?