Display went off after resume from LCD off

I usually leave my computer on for around 5 ~ 7 hours per day. And some time
between that, i idle and let the computer finish the job. Something like
Scaning for Virus.

The settings for Power Management set as -
Plugged in: LCD off in 20minute
Hard Disk (Turn off): Never

Whenever i resume(Press space/Move Mouse) after the LCD it was already
turned off, the screen blanks once and it's back off. On my other computer,
it's LCD turns on normally. However, it's different, it seemed like the LCD
IS on but the brightness level is down to nearly 5%(estimate). Manually, the
lowest brightness level is around 40%. I had to focus my light toward it to
see VERY little of what's on the screen.

For what i do now to fix this ...is close down the monitor (it's a laptop)
and let it be in sleep mode for around 20seconds, then open the monitor
....and back to normal. However, i feel frustrated when i need to do that all
the time. It also disconnect any download or any program that was running.

Please, if anyone know what the problem is, guide me !