User-Agent:       Mozilla/5.0 (X11; U; Linux i686; en-GB; rv:1.9.2.12) Gecko/20101026 SUSE/3.6.12-0.7.1 Firefox/3.6.12

When attempting to connect to a valid MSN account, Pidgin gives the error message "The certificate for omega.contacts.msn.com" could not be validated.  The certificate chain presented is invalid."

This problem has been reported in the Pidgin ticket system here: http://developer.pidgin.im/ticket/12906

To summarise the discussion:

MSN's contacts server is misconfigured with respect to intermediate certificate authorities, so Pidgin ships MSN's intermediate certificates in-built.  Microsoft have just updated their certificates, thus this problem.  However, there is also a bug in the way Pidgin is handling certificates.  The issue is allegedly fixed in Pidgin 2.7.7 and a backport was specifically mentioned as being perfectly possible.

Reproducible: Always

Steps to Reproduce:
Happens (almost) every time.  Ratio of failures to successful connections is about 20:1

1. Add MSN account details to Pidgin
2. Save and attempt to connect to MSN
3.
Actual Results:  
An error dialogue is presented with the text "The certificate for omega.contacts.msn.com" could not be validated.  The certificate chain presented is invalid."  MSN is unable to retrieve the user's contacts list and will not log in.

Expected Results:  
MSN logs in and the Contacts list is retrieved and displayed.