I Cant Log-In On MultiPlayer

i do not know why, and i need big help. i mean i can log on and get on the forums and stay logged-in but when i click play the game button, it logs me out, and when i go to sign in again it just brings me right back. i have the same problem with hotmail. and it makes me very frustrated. i cant log in!! i want to play MP really bad. can someone please help me. it just keeps brining me back to the log-in screen, and yes the account name and password is correct, cus i can get on here. i don't know if its my browser or anything. i use internet 7, or it could be cookies blocking me? i'm really not sure and i need help. my privacy security is mcafee.

help me please?

-ClockTower.