I had the exact problem and ended up getting support to delete the user completely for me. Initially the bloke said it'd filter through the system after a few hours, but when that didn't happen I asked him to remove the user manually. He happily complied.
If you look under the UNIX GROUPS tab, the user is still listed there in the group. I don't know much about unix groups and all that jazz, but if the user is still listed there, then it's registered.
Aaaanyway, contact Support. They've been heaps helpful for me and they fixed it up.
Some cause happiness wherever they go, others whenever they go. - Oscar Wilde