This error is usually caused by the security parts in MSN Messenger not working correctly
First, you can try to register the dll files which Messenger needs. Registering them allow Windows to tell Messenger where it can find them. In addition, this also trigger the addition of certificates to your computer's certificate store. Certificates are used by MSN Messenger to encrypt your password when it is send to MSN for validation.
Download and execute
this file to do this automatically.
First open a run window by clicking start, then run. Now, type the following command and press enter:
regsvr32 softpub.dll Wintrust.dll Initpki.dll Rsaenh.dll Mssip32.dll Cryptdlg.dll
If you use Windows XP you should open another run window after running the previous commands then type the following command:
regsvr32 Dssenh.dll Gpkcsp.dll Slbcsp.dll Sccbase.dll
If this does not solve your problem, try the following: close Messenger then go to
www.passport.net with Internet Explorer (also if you normally use another webbrowser) then click on the sign in button, you may get a certificate dialog. Accept the certificate, now if you start MSN Messenger it should work.
If you did not get the certificate dialog and MSN Messenger still does not work, open the advanced settings dialog in Internet Explorer by clicking on the Tools - Internet options menu and then go to the advanced tab. Go down to the security section and make sure
use SSL 2.0 and
use SSL 3.0 are both checked. MSN Messenger requires SSL for the authentication process (checking if your username and password are correct).