POSSIBLE SOLUTION that worked for me!!!
If you have installed teamviewer and the teamviewer's driver
provided for your screen (that it is can be done from advanced settings in version 6) RESTORE IT to the previous monitor driver and it will work instantly!!!!
If you don't know if the driver is installed just locate the monitor in device manager. The teamviewer's driver is named teamviewer monitor driver or something like that... It was for me easy enough to understand the difference...
Well at this point just RESTORE PREVIOUS MONITOR DRIVER (NO UNISTALL) in 7 (or xp or vista)
For all others that DO NOT HAVE TEAMVIEWER installed I suggest to reinstall the ORIGINAL MONITOR DRIVERS
and NOT DISPLAY DRIVERS CARDS brightness control seems to be depended from monitor drivers.
Please add the solutions that were found in topic start.