I've been asked to file a bug by the Empathy developers, after originally filing a bug in Empathy:

https://bugzilla.gnome.org/show_bug.cgi?id=672542

I noticed that one of my MSN contacts was missing in Empathy. Having searched
around to find where gnome-contacts stores my contact information, I confirmed
by grepping that the identifier of that contact was missing. So, I tried to use
Chat→Add Contact… to add the contact. When I click "Add" I get no error
message, but the contact is not added.

I'm running Empathy 3.3.92 as shipped in Ubuntu 12.04 (currently in beta).

As asked in the original bug report, here's what the debug log says when I try to create a contact:

purple/msn-INFO: 21/03/12 14:38:28.725136: C: NS 000: PNG
purple/msn-INFO: 21/03/12 14:38:28.725248: C: NS 000: PNG
purple/msn-INFO: 21/03/12 14:38:28.879102: S: NS 000: QNG 44
purple/msn-INFO: 21/03/12 14:38:28.880790: S: NS 000: QNG 50

I can't be sure that this output is directly related to the contact creation attempt, but it's the only haze output appearing in the debug log when set to level "Info" at about the same time.