I have a MacBook and am running Tiger Mac OS X 10.4.6 and no matter what browser I use, my browsers keep closing occasionally when I click on a link to enter a website. The page will be loading and suddenly, in the blink of an eye, the browser will have quit and I'll get a prompt to retry. When I retry, I have to be sure and x out of the troublesome link or it will do it again indefinitely. This started out being very rare and has become very often lately. What is the cause of this problem and what can I do about it?