If you can't sign in to MSN Messenger, the connection settings in MSN Messenger might be preventing you from connecting to the Microsoft® .NET Passport or Microsoft® .NET Messenger Service. The MSN Messenger Connection Troubleshooter can often find and fix these problems. The Connection Troubleshooter starts automatically if MSN Messenger encounters a connection problem. If you choose not to use the Connection Troubleshooter, or it does not solve your connection problem, try the following:
1. Click the Tools menu, and then click Options.
2. In the left pane, click Connection.
3. Under Connection Settings, click Test Connection.
If you agree to allow the Connection Troubleshooter to examine your system, it will test for connection problems and report steps you can take to correct them.
4. Optional: Perform advanced troubleshooting
To troubleshoot your specific type of connection, click Advanced Settings. On the Advanced Connection Options dialog box, check that the settings for your particular connection type are correct. To test your connection, click the Test button. Click OK, and then click OK.
5. Click OK.
When you choose these settings, MSN Messenger will use the Microsoft® Internet Explorer connection settings if possible.
6. Try signing in to MSN Messenger again.
You should know if you have a firewall,do you recollect downloading one?If not then you will be running the Windows firewall which wont prevent MSN from loading. I have heard,and try it, that if you go to your clock in the bottom corner,double click on it and check to see if the time,date and year are correct,if not then correct them,if they are then alter them to whatever and try to sign in,If,and that is a BIG if,this solves your problem,then once you get into MSN,alter your clock to the correct time,close out of msn and reboot the pc and try logging on again to see if the problem has gone. If that fails,i can only think its a virus and i would advise doing a full virus scan, and also download ewido anti-malware and spybot search and destroy (you can find them in the forums on how to protect your pc) and run them and delete any nasties they find. If non of this helps then i really dont know im afraid.
Let me know if anythings worked