Can't sign into msn messenger

Hi,
When i try to sign on to my msn messenger account it
says i have forgotten my password or my username is
invalid. Then my sister tried to sign onto hers and it
said the same thing. It also said the same thing when my
mom tried to sign on to her account. I have tried
reinstalling msn messenger but that didn't work, I tried
creating a new account but that didn't work either. What
do I do?????

Ben