Lose Internet connection

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?

I'm not sure if I can answer your question, but maybe provide some insight.

When Ubu launches a background process, like installing new software or performing an update, the screen fades out during the install to prevent you from doing anything at that critical time. So that's what's going on there.

If the system is "greaying out" while doing online stuff, I suspect Ubu is trying to install some app/resource, failing, and crashing your program.

I don't use Thunderbird myself, though I don't know what Firefox needs that Thunderbird might share.

I'm in Windows at the moment, so reply to this message and I'll jump into Linux to see if I can be of more help.

(BTW: I'm using the 64bit Ubuntu 8.04, so my results my vary.) :)