brightness is low

I have upgraded from 11.3 to 11.4 with KDE. It is a64-bit version of OS. I am happy that almost everything is working fine. The screen brightness is too low. From boot until the login screen, the brightness is perfect but soon after logging in brightness dramatically reduces. I have set the brightness to maximum in power management profiles, but the maximum brightness itself is too low.

I am using MACbook Pro 7.1 with NVIDIA graphic card. I did not have issues with 11.3. I have updated everything after the initial upgradation.

Any suggestions ?

Thanks in advance.

I have had this same problem with a Dell Vostro; I thought the screen had died until I tried booting the Windows Restore disk and the screen immediately was rejuvenated. I re-installed 11.4 as 32 bit and am testing this version - so far no serious issues except the suspend does not seem to work when closing laptop lid, but no screen or freezing issues with 32 bit… Also I think KDE may be at play with the screen issue.