help configuring a 30" apple cinema display

[Robby Findler]

Hi all: I'm having some trouble getting my apple cinema displays to
run properly. I have two of them, a 23" one (DVI0) and a 30" one
(DVI1). here's the output from xrandr:

----
Screen 0: minimum 320 x 200, current 3200 x 1200, maximum 4480 x 1600
VGA1 disconnected
DVI0 connected 1920x1200+0+0 495mm x 310mm
   1920x1200      59.9*+   60.0
VGA2 disconnected
DVI1 connected 1280x800+1920+400 641mm x 401mm
   1280x800       59.9*
----

which I think means I need to add a mode to get the DVI1 one to
2560x1600. So I did this:

xrandr --output DVI1 --newmode 2560x1600 348.50 2560 2760 3032 3504
1600 1603 1609 1658 -hsync +vsync

which seemed to succed, but then I get this:

  xrandr --output DVI1 --mode 2560x1600
  xrandr: cannot find mode 2560x1600

Any ideas what I'm doing wrong?

Thanks,
Robby