On the 512mb-
I had that problem for a while but i just fiddled with it for a bit - 
Menu - "sys.thingy" - backlight options (there are two different backlight settings, chose the second) - edit to different numbers. 
Mine now stays a tastefull green (::
All i need to do now is find some firmware since the main site seems to be down...
                
 LcR
                
 October 2005