You will see this on an otherwise blank screen. Assuming that the data cable is plugged in correctly, the video card is feeding the monitor a signal stream in excess of what the monitor can accommodate. The two main causes for this are that the user has set either the resolution or the vertical frequency rate too high. For example, you might set a new graphics card to display at 1280 x 1024, but if the monitor is only capable of 1024 x 768 resolution, you’ll get a Sync Out of Range error. This is especially common in 14-inch monitors.
In windows you would reset this by going to safe mode. Not sure with Xandros.