Crc corruption when attempting to create java.awt.image.

I get an odd exception when my applet attempts to create a java.awt.image from a PNG file. I can't see what it is that I'm doing wrong :(

This is the interesting bit of the stack trace:
sun.awt.image.PNGImageDecoder$PNGException: crc corruption
      at sun.awt.image.PNGImageDecoder.getChunk(PNGImageDecoder.java:719)
      at sun.awt.image.PNGImageDecoder.getData(PNGImageDecoder.java:727)
      at sun.awt.image.PNGImageDecoder.produceImage(PNGImageDecoder.java:249)
      at sun.awt.image.InputStreamImageSource.doFetch(InputStreamImageSource.java:257)
      at sun.awt.image.ImageFetcher.fetchloop(ImageFetcher.java:168)
      at sun.awt.image.ImageFetcher.run(ImageFetcher.java:136)

I write out the buffer length that I get from the inputstream, and it is the same size as the PNG file. So I assume that my code has read all of the available data.

I've shortened the code that does this below, removing only the printStrackTrace() calls and log messages.

    String s = "image.png";
    InputStream in = getClass().getResourceAsStream(s);
    if (in == null) {
      System.err.println("Error. " + s + " file missing");
    }
    try {
      buffer = new byte[in.available()];
    } catch (IOException e) {
      System.err.println("Error. " + s + " size count error");
    }
    try {
      in.read(buffer);
    } catch (IOException e) {
      System.err.println("Error. " + s + " read error");
    }

    image = Toolkit.getDefaultToolkit().createImage(buffer);
    tracker.addImage(image, 1);

    try {
      tracker.waitForAll();
    } catch (InterruptedException e) {
    }

Any ideas?