Unable to Adjust Screen Brightness on Sony VGN-NR21Z running Suse 10.3

I have bought a copy of Open Suse (310059239/10) and am running it on a 
Sony VGN-NR21Z.  Mostly it works very well, but one of two things I am 
having difficulty with is adjusting the screen brightness.  The screen 
brightness controls are the keys (Fn. and F5) to reduce and (Fn. and F6) 
to increase.  Under Suse 10.3, these controls do not work.  The graphics 
card is an NVidia GeForce 8400M GT.  Do you know what I can do to reduce 
the brightness?  I have tried installing one suggestion (smartdimmer) 
but that did not work.  Do you have any suggestions?

If anyone could help, I would be very grateful.  Regards,
William Portal.