why was my facebook chat disabled?

okay so last weekend i was online and supposed to be doing homework and i was getting distracted over the facebook chat, so i went off line. i then i logged off without putting my self back online. ever scince then i have not been able to access the facebook chat, everytime i try it tells me that for that page it is disabled. i relize that some parts don't let you but this is EVERYWHERE, ever on my homepage. i have gotten complants from my friends that they can not get me through facebook chat, please help me i want it back!!!! plus along with this i am not able to see who is online. i'm really pissed off now