My second 770 screen died within a week of me receiving it, and I noticed the screen flickered but only when the backlight was off.

I'm wondering if the buzzing leads to the flickering which then leads to the screen giving up ?

You mentioned the buzzing goes away at max brightness. That might explain why some 770's seem to last longer than others, I leave the brightness at about 50% as it comes out the box and my 2 770's have died within a week, others might run them at 100% brightness and so avoid the problem ?

Anyone with a 770 they have bought within the last month that is still OK despite running the screen at less than 100% brightness ?

I really wish Nokia would sort out this problem themselves. They have said nothing as far as I know about this hardware problem. If I've had 2 go this is a very common problem indeed.