I was playing Monopoly as a guest at the above URL when WebKit.app crashed. I do not recall getting crashes in Safari 3.2.1 or Firefox 3.0.6 while playing the same game on the same machine. Since there is a character size limit in the problem description field, I will attempt to attach the crash log after saving this bug.
Created attachment 27472 [details] WebKit crash log
The crashing thread is deep inside the JVM. This is almost certainly not a WebKit issue. You should file a bug report at <http://bugreport.apple.com/> so that it can be investigated by the Java folks.