Re screen flicker - Its caused by a harmonic of the busts of data sent on GSM. Although the data is sent at 900Mhz or 1800Mhz (or 850 or 1900 in the US), it is sent in bursts and not in one continuous wave. The frequency of the bursts has harmonics in the Hz spectrum, which is the same range as the refresh rate of the screen.
Primarily this results from poor shielding in the phone, or a shared ground plane between Hz sensative components and the radio baseband. Its not something that can be corected by software, and a design fault.
You would expect to see this with bot EDGE and GPRS as they both use GSM. Its unlikely you would see this with UMTS tho.
RE brightness issue - it might be causes by a faulty light sensor on your phone. If you look carefully under a bright light you'll see that there is a light sensor just to the right of the ear speaker. You should keep your finger over this, or hold the phone under a bright light and see if there is any difference. You should also turn off auto brightness from the settings menu in android and see if the same repeats.
If it does the same with auto brightness off, then its not the sensor, and could be a charge pump issue with the screen. If it doesnt then either its probably that sensor. Covering and testing with a bright light will offer more proof or disproof to that tho.
|