It hasn't happened before and I can't get it to happen again but I got it when I deleted an account. HFS didn't crash or anything and the account deleted correctly, so it isn't a major problem.
If it helps, some parameters were that the name was in all caps, it redirected to a nonexistant folder, it had a password without special characters, and wasn't a member of a group. Recreating an account with the same parameters doesn't reproduce it, so I don't know.
EDIT: Wait! I got it to happen again. I think it occurs if you delete an account directly after changing the password of another.
EDIT 2: Yes, I verified that for me at least, the error occurs if you delete an account right after changing another account's password.