// Revision 1.0.1
// Mac OS 10.4 / 10.5
// When a semitransparent rect should be drawn (once) over an image
// the rect is instead re-drawn everytime void draw is executed.
// This leads to a fading effect, when instead the rect is not supposed not
change.

PImage img;
boolean firsttime=true;
void setup()
{
size(200,200);
img = loadImage("milan_rubbish.jpg");
background(255);
fill(0,128);
}

void draw()
{
if (firsttime) {
//draw left image once, overlay a semitransparent rect
copy(img,10,50,80,80, 10,50,80,80);
rect(10,50,80,80);
firsttime=false;
} else {
//draw right image repeatedly, overlay a semitransparent rect
copy(img,110,50,80,80, 110,50,80,80);
rect(110,50,80,80);
}

}

please use tools > archive sketch to create a zip file and attach the
sketch here.

please also update to 1.0.5 to make sure that it's not something that's
been fixed in the meantime.

// also for Revision 1.0.5
// sorry ;)

I still need the sketch to fix this.

edit]
zip file with a patch, including data folder

there you go.
its the same code as posted in the bug description.
Thanks for your concern!

Andres