When this happens to me I try 2 things. First I reset the game by highlighting the address bar and hitting "Enter". This takes you out of the game and brings you back with your browser freshened. Second, rather than turning off your computer for about 30 minutes to let it cool down, I get an Ice Pack from the freezer and place it under the left side of my laptop. One of these will almost always work.
Dusting and cleaning the computer fan helps also.
(Hi Steve)