I doubt that there are many D-Viewcam users out there using a 2560x1600 display,
I wasn't able to find anything online about this issue but it's been here for a while.
I've changed three computers in the last 3 years (using the same Apple Cinema Display 30") and the problem has always been present, Windows XP, Windows 7.
I don't expect them to fix this but i thought someone who could do something actually paid attention to these forums.
I'm currently using D-Viewcam 3.3 as all the links to 3.5 are apparently dead or some kind of false files.