Help. x1600, dual monitors, DVI twitching

[Ron King]

Hi,
I'm on Fedora 11, M56 x1600, X server 1.6.2-3, ATI driver 6.12.2-14.  
Laptop with docking station and dual Samsung SyncMaster 940Be LCDs.  
Docking station has one VGA and one DVI-D.  All works fine in XP, Fedora 
8 (using Xrandr 1.2, I believe).

LVDS and VGA work fine, alone or dual.  DVI produces a vertical twitch, 
always.  Running the cursor up the screen shows missing horizontal 
lines.  Modes appear to be correct and match published monitor modes.  
Changing modelines with xorg.conf and Xrandr do not seem to have any 
effects.  Adding modes in Xrandr and using them causes the monitor to 
blank, then return and still report the same problem.   Monitor reports 
31.7kHz and 30Hz regardless of changes.  Is this mode hard coded for 
DVI-D somewhere?

Please advise and thanks...Ron