Prevent maximum screen brightness in lockscreen? I've set my screen brightness to about 50%. This works fine for me, except that the setting seems to be ignored while displaying the lockscreen while being charged: then it's 100%. I've got a desktop charging stand on my bedside table, and this is exactly the place where I don't need maximum brightness!

How can I make my iPhone respect the brightness setting even when locked and charging?

This is an iPhone 4 with iOS 4.2.1. In an earlier question, I asked about the brightness while charging - but this question is specifically about the lockscreen brightness.

It's already jailbroken so suggestions in that genre are fine too.

Update:
The auto-brightness setting is ON because I like that it dims at night but goes bright during the day; I have tried it OFF but I had to adjust the brightness manually too often during every day. I'm not aware of any jailbreak-specific setting regarding brightness.
iOS 4 and 5 were notorious for having this issue. They frequently ignored the ambient light sensor and were so stubborn, they refused to adjust the screen brightness to compensate. iOS 6 has corrected this issue.