help needed! a bug in the acp -> manage users

hello there.
all i wanted to do is to change the name of one of my users.
so i entered the acp -> manage users -> manage
i looked for the username and found it
but when i get the form with all the user's detail, something very strange is happening.
i see all the user detail, but after a second, the username and password is changing to mine!!!
i tried another user, the same problem....
i cant figure out why is it happening/
it is not the first time i am trying to change usernames, but i think since i have removed prillian this thing has happend
please anybody help me or give me a clue.
i dont know what to do
thanks
all i wanted to do is to change the name of one of my users.
so i entered the acp -> manage users -> manage
i looked for the username and found it
but when i get the form with all the user's detail, something very strange is happening.
i see all the user detail, but after a second, the username and password is changing to mine!!!
i tried another user, the same problem....
i cant figure out why is it happening/
it is not the first time i am trying to change usernames, but i think since i have removed prillian this thing has happend
please anybody help me or give me a clue.
i dont know what to do
thanks