Canon EOS 20D EOS DIGITAL Software Instruction Manual (EOS Viewer Utility 1.2. - Page 216

Troubleshooting When the "Communication between the camera and computer failed" or "Software not running correctly" message appears, check the items described below. I have installed the software but the camera and computer cannot communicate. O Does your computer comply with these requirements? J A Macintosh with a FireWire (IEEE1394) connector as a standard feature. * Operation is not guaranteed when the camera is connected to a FireWire (IEEE1394) interface that is not a standard feature of Macintosh. O Are the camera and computer connected correctly? J Connect the camera to your computer correctly using the dedicated cable (M-8). O Is there sufficient charge left in the camera battery? J Your computer does not supply power to the camera. Connect the DC Coupler Kit to the camera or load a fully charged battery into the camera before connecting it to your computer. O Do you have more than one camera connected to your computer? If you connect more than one camera to the same computer, the driver and camera may not operate normally. J Quit the software and disconnect all the dedicated cables. Then connect only one camera to the same computer again. M-98