Q: Snow Leopard update makes my MacBook Pro overheat

I have just updated my early 2011 MacBook Pro to Snow Leopard but now when I run the browser the fan runs like crazy, and then the computer overheats, and then the browser hangs and I have to force shutdown to stop the racing of the computer.  What is wrong?  This is an older computer on an older operating system, so this should not be a new problem, but I cannot find anything in the community history about it.  P;ease help!