dunno man.. if its the same thing as me, i think its definitely something to do with zclient.exe - some of the old clients i used wouldnt open up or connected but didnt auth, so i tried another and i noticed it gave a warning about making sure client was named Zclient.exe so i deleted all of them, downloaded a new through .tk/faq and clicked it through downloaded files folder, updated and now playing :s
Reboot, delete old clients, move client to desktop, rename to something else and rename to Zclient.exe again etc.. SOMTHING MUST WORK!