Yeah, there is a program made by someone on this forum that makes the crackle disappear. The application itself is called XPS Lights, but it's only available on windows XP.
I have the beta version of the vista one, PM me with your...
Might be the brightness of the computer went from bright to dark? Dunno, that would've been my best guess, but yeah it's probably wrong.
I'd go get another replacement from dell cause something is seriously wrong =/