If you're projecting through your computer's USB port, make sure the USB Type B setting in the Extended menu is set to USB Display. See Customizing Power and Operation.
With Windows, you may need to install the USB display drivers manually by clicking My Computer or Computer > EPSON_PJ_UD > EMP_UDSE.EXE. If nothing is projected after the USB display drivers are installed, click All Programs or Programs > EPSON Projector > EPSON USB Diaplay > EPSON USB Diaplay Vx.x on your computer.
With Mac OS X, click the USB Display icon in the Dock. If there is no USB Display icon in the Dock, open the USB Display folder in the Applications folder and run USB Display.
If you see a black screen and you are connected through your computer's USB port (or through your network), the application may be using DirectX drawing features, which are not supported.