The internet seems to be very confused about accessing download mode in the Samsung Galaxy S II released by AT&T.
It is actually simple to enter download mode:
1. Power the phone off.
2. Plug the usb cable into the computer (not the phone)
3. Hold both sides of the volume rocker down (vol up + vol down)
4. While holding those buttons down, insert the usb cable.
There is no need to touch the power button on the phone to enter download-mode on this device.
For those of you who are quick learners:
Insert the USB cable while holding the volume rocker down with the phone off.
This works on the Samsung Galaxy S II released by AT&T on October 2, 2011, model SGH-I777
