When you create two X servers on Linux (which usually can be switched via Ctrl+Alt+F7 and F8), switch to one of them and run the following code against the other:

import java.awt.Rectangle;
import java.awt.Robot;
import java.awt.Toolkit;
import java.awt.image.BufferedImage;
import java.io.OutputStream;
import java.io.FileOutputStream;
import java.io.BufferedOutputStream;
import java.io.File;

import javax.imageio.ImageIO;
import javax.imageio.stream.FileImageOutputStream;
import javax.imageio.stream.ImageOutputStream;
import javax.imageio.ImageWriter;

public class AWTBug {
        public static void main(String[] args) throws Exception {
                Robot robot = new Robot();
                BufferedImage src = robot.createScreenCapture(new Rectangle(0, 0, 100, 100));
                ImageWriter iw = (ImageWriter) ImageIO.getImageWritersBySuffix("png").next();
                ImageOutputStream os = new FileImageOutputStream(new File("image" + System.getenv("DISPLAY").replace(':', '_') + ".png"));
                iw.setOutput(os);
                iw.write(src);
                iw.dispose();
                os.close();
        }
}

...the captured image contaings a lot of garbage (mostly black or random pixels).

The bug seems to be in the capturing code, because when we capture images in a loop and compare them, most of them are different from each other.

The same bug occurs on solaris-sparcv9, solaris-i586 and linux-i586 (haven't tried the other platforms).