full brightness @ bootup

[Fazzy]

every time i boot up my macbook air, it starts at full brightness for some reason, even though I never have it past half. Why is this?

 

[Bigtree]

My iMac does it all the time. I have to unplug everything and hold the start button for 20 seconds to clear it. I wondering too why it does this.

 

[swaroop.ms]

Resetting the PRAM worked for me.