Just about to calibrate my new twin head X11 Ubuntu Linux 64 bit AMD system, running two DVI interfaced flat screens with the Xinerama extension. Runnning dispwin shows the colour squares on both displays (choose with -d option), but the screen doesn't darken or lighten at the end of the sequence. I take this to mean that the LUT isn't being updated by the program. Before I look into this further, are there any known issues with the Matrox P650 card and Argyll? As far as I know, the card is supposed to have two LUTs, one for each output channel. One of several reasons that I selected it... Neil