I've seen misbehavior similar to this bug that turned out to have a cause not listed here.
If you have a monitor capable of 20048x1536 resolution, X 7.3 will ignore the high-res modelines it gets from EDID complaining that the vertical size of the mode is too large for the virtual desktop size. This problem is due to a poor choice of default virtual-desktop size and can be fixes with an explicit Virtual declaration; I use "Virtual 2048 1536".
I've seen misbehavior similar to this bug that turned out to have a cause not listed here.
If you have a monitor capable of 20048x1536 resolution, X 7.3 will ignore the high-res modelines it gets from EDID complaining that the vertical size of the mode is too large for the virtual desktop size. This problem is due to a poor choice of default virtual-desktop size and can be fixes with an explicit Virtual declaration; I use "Virtual 2048 1536".