FC8 (32-bit) screen dimming

[Phillip]

On upgrading from FC6 to FC8 on my laptop, the screen dims almost 
immediately at the beginning of the boot up sequence. The screen is bright 
for any length of time until the messages shows that the kernel is 
booting. Then the screen dims so that text and graphics are barely 
discernible. This is true in text as well as graphics modes (runlevels 3 
and 5).

Does anyone know what setup file may be causing this?

Phillip Thomas