I am on OSX Lion, with a MacBook Pro. I am using the DisplayPort for an external monitor and two USB Diamond BVU195 for two extra monitors. Each time when I turn my computer on, the two monitors get mixed up/reversed - so instead of going from left to right, like this:
MBP Screen | BVU195 - 1 | DisplayPort | BVU195 - 2
It shows up wrong like this:
MBP Screen | BVU195 - 2 | DisplayPort | BVU195 - 1
It is easily fixable by going to System Preferences and reversing them, but next reboot, they are mixed up again.