Brightness control not working. Bootcamp 8.1 rMBP 13'

Hello!

Id appreciate some help with the following

What happened:

1. I installed windows 8.1 on my new *yesterday bought* rMBP
2. Everything was working fine, although the brightness contol used the default windows slider.
3. Windows updated
4. The brightness control no longer worked. They showed the windows slider moving but that did nothing, manual movement of the slider didnt work either.

Fixes attempted:

1. Reboot
2. Disable adaptive brightness
3. Repair Bootcamp drivers
4. Reinstall OSX from recovery and re-doing bootcamp
   1. Disabled windows update in the installation menu
   2. Disabled automatic driver fetch in the installation menu

Post troubleshoot:

1. Brightness controls in windows dont even show the windows slider anymore
2. Moving the slider manually does NOT work.

Fixes attempted:

Disabled adaptive brightness in windows

Post troubleshoot x2:

1. The slider is back when I use the brightness keys.
2. Still no actual brightness change.

Misc info:

1. OSX Mavericks (Fully updated)
2. Windows 8.1
3. Specs
   1. 8 GB ram
   2. 256 HDD
   3. 13 inch
   4. late 2013 (purchased yesterday)
   5. Spanish (ISO) keyboard.

Id be glad to provide any more information you require.

Thanks for your time, Salomon