Okay, I have seen a couple of people mention that they don't know how to send private messages since Core Connect was released. This used to be as simple as clicking on the name under the avatar of the person you wanted to contact. Now, however, that redirects you to the Core Connect User Profile of the person you want to contact.
1. What you are going to have to do to send a private message to another player on the forums is write down their name and server EXACTLY as they appear on their post tabs.
2. Then, go to your User Control Panel and find "Send New Message".
3. Click on that, and it will take you to your New Message screen.
4. Input the name and server you wrote down earlier into the "Send to" space (should look something like this: KrittyCat - Dreamweaver) then proceed as normal.
Your message should go through without a hitch!
Hope this helps!
(Signature credit to NowItsAwn)
Survivor of Snow-Mageddon 2010, "The Great Earthquake" of 2011, and Sandy 2012 b:victory