Finaly I got ATT 0.27b4 to work with my HD3850-512. Here is the trick: In the system services management console, you'll find "ATI Hotkey Poller" service. If you want to use ATT for OC your HD38xx, disable this service since that one is used by the driver to detect the 2D/3D changes and conflict with ATT 0.27b4. After you disabled this service, reboot your PC. Now, your HD38xx should use only the max default clocks depending on your card model and manufacturer (no more powerplay). From now ATT 0.27b4 can be launched but, first of all, you have to configure it. Go settings, open the "HD2000 Overclocking" and uncheck the "If the card has 2D/3D clocks, switch to 3D clocks when starting ATITool". You're set. Now you can change the GPU/MEM clocks as you wish and even try to find the max clocks.