Recently I've notice that while either writing an email(Thunderbird) or on the Internet(Firefox), the screens dims down and loses the color and sits there for about 30 seconds and then switches back to my desktop and I lose my email, if writing something, or closes the webpage I was previously on. I am still with Ubuntu 7.10. A window then appears telling me that it is Not Responding. Why is this happening now and what could be the causes of dropping the connection? Anyone?