Shoutbox

If it is still not working you could try the following;

Try changing servers by downloading msnservers.zip. If you are using a version of windows before XP or haven't already got WinZip download and install WinZip from www.winzip.com. To be able to open that file.
Extract all the contents of that file to the desktop and open the msnservers.exe file. Select another server, test it, and change to it and then try and sign in again.

If that doesn't work please could you tell us
Are using a router?
Are you using a firewall?
If yes, please state the name and version number of the firewall.