Why does my system dim and go grey sometimes?

[mark Pyles]

Hi everyone:

I am using Unbuntu 8.04 (gnome desktop) on a Dell Inspiron 1525 laptop 
and wanted to know why is it that sometimes whenever I am reviewing a 
webpage or email or anything else that my screen seemss to dim and go 
grey? I have  3 gigs of ram so I would have thought that would be more 
than enough? Is there something I can do to fix that? Thanks.


Mark