'Multiplayer option?' Are you that you're not just trying to go online from the single player game? Are you using the in-game browser when you should really be using xfire?
You can find the updates
HERE.
I actually bought 'Best of PC' around Christmas time. I didn't install JK2 (since it already was) but I did install BattleFront. I could only play on 2 servers, the rest were greyed out. I also had trouble updating it, which I posted about here:
http://www.lucasforums.com/showthread.php?t=172967