You can try clearing the cookies and temp files of your browser.
You can try using the latest versions of chrome or firefox and NOT internet explorer.
You can try updating your java but this is usually not the case.
If none of these don't work, then give more info on your system so we can help you better.
recently I started to have visualization problems in playing live games,as I join a game a big empty chessboard sobsitute the smaller one(the smaller pieces remain) and the game never start:do you know if I can do some to avoid that?