I have four monitors that each have a resolution of 2560 x 1440. These monitors were originally arranged in a box layout, two on top and two below. In this configuration, my Ubuntu guest virtual machines were able to use all four monitors. My Ubuntu VMs are configured with 3GB of Graphics Memory and Accelerate 3D graphics is enabled.
On the host machine, I changed the monitor arrangement to have all monitors side by side in one row. When I put my Ubuntu guests in full screen mode and attempt to have them use all monitors, I get an error dialog stating "The virtual machine could not be changed to the selected monitor layout. If you just added a monitor to the host computer, you must power off and power on the virtual machine to use that monitor." If I try to get the Ubuntu guest to only use three monitors, it works. These are the same four monitors that were arranged in the box layout. If I change the monitors back to the box layout, the Ubuntu guests can use all four monitors. When I switch back to the single row configuration, I can only use three. All guests have vm-tools installed. I've tried this on multiples guests, multiple host computers, fresh installs of Ubuntu, and even different flavors of Ubuntu (Ubuntu, Lubuntu, Xubuntu). All produce the same result.
Does anyone have any idea how I can resolve this so that I can use all 4 monitors when my four 2560 x 1440 monitors are arranged in a single row?