If the UI is client side, why is it that when I log into my 1440 x 900 laptop I have to move my map in from the right edge and my action bar in from the very bottom edge, then when I log into my 1920 x 1200 PC I have to drag the map and action bar practically out of the middle of my screen? If the UI was client side, moving the UI pieces on one system would have absolutely no effect on the other.
Your mini-MAP graphics are client side, but your position of your mini-MAP are stored on the server. Some MMO developers do this, never understood why though.
You can also compare this when you log out. Your character position in the world is stored on the server, while your character graphics is stored on your PC.
So when you want to trade, your UI is coming from your PC, but the containing data needs to be retrieved from the server. As long as the data ain't completely retrieved, your UI won't show. This is called lag what everyone is complaining about. Edited, Sep 10th 2010 5:36am by Shoomy