Hmm... If Mo is the sole person you want to have a conversation with, then I'd recommend the following.
1 Click on the link for Mo's name, that'll take you to that member's profile snapshot.
2 The snapshot profile should contain the member's name, title, gender, age, location, status quote, and links to visit their Profile Page and Start a Conversation.
3 Click on the link to Start a Conversation with Mo directly.
4 This will take you to the "Start a Conversation" page where Mo's name will already appear in the Participants edit field. Just add the title and message in the appropriate fields, and then click on the Start Conversation link.
If this still doesn't work, it may be that Mo has their own settings in place so as not to receive any conversations through the forums. You'd have to set a thread for this like "Paging Mo" or something to that effect.
Hope this helps.