You may need to lower your game resolution. This can be done by clicking the gear shaped icon on the top bar in the lobby and changing it from HIGH to MED or LOW. Lowering the resolution will reduce the number of animations in your game, which will help the game run better on certain computer systems. We also recommend that you regularly clear your cache, and completely close and re-open your browser. It's best if you don't have multiple browser tabs or browser windows open, as this can reduce the amount of memory available to the game.
If you continue to have problems, you might also want to try re-installing your flash player; sometimes a plug-in in your flash player can cause loading issues. To re-install your flash player, please go to this link: http://get.adobe.com/flashplayer/