I get that same message on my displays and haven't really found a good solution. I have been able to still order the monitors via the windows display properties and dragging them to correct order, but it is still pretty much guess and check and no guarantee that it will boot up that way. Between the monitors becoming unordered and my screens losing connectivity, the whole project has been a pain in the ass to manage.
My setup consists of 7 separate PC's running multiple fireglide cards as well. Four machines push 2x6 panels, two machines push 1x10, and the last one spans across the 70 inch screens on the outside (the are running cable now though). The panel TV's are all 42 inchers.