I use Pidgin (now in version 2.7.5) in its Portable avatar. Because its so easy to transfer my text-only IM (instant messaging) accounts from MSN, Google, Yahoo and AOL between computers. Or between locations via a pen drive.
If you too use Pidgin and have recently found that you can’t sign-in to MSN. Instead you keep seeing an error associated with the omega.contacts.msn certificate. Don’t be quick to blame the Pidgin development team. The problem is caused by Microsoft updating its security certificates.
For more details on the problem including how to effect a resolution got to Andrei Neculau authored Pidgin and MSN (certificate error for omega?.con?tacts?.msn?.com).
Make sure to read carefully though the comments as well.