Alpha client display bug

After updating to this new client, there has been a display issue. Starting from loading-in-game, my screen kept flashing black, but the loading progress is fine. While in the game, the display was really dark and was flicking most of the time. Turning on the vertical sync setting resolved the vertical flashing of black part, but the display was still not normal. Adjusting the quality or fps or resolution did not seem to help. Help please!