OK, thanks for the answers and additional checking. Your observation on the laptop is particularly helpful. [I assume you're using the built-in laptop screen rather than an external monitor?] You're reasoning seems solid about the monitors - you are observing the same symptom on two entirely different monitors, so the problem is somewhere else.
Unfortunately, the 5 different systems that I can use to test all have ATI video cards, and not very new ones at that (1 to 2 years old). They have different monitors, and one of the systems is an HP laptop.
The largest monitor is a 22-inch Acer LCD, and the smallest is a 15-inch CRT. None of the connections is HDMI.
I have never (including Beta 6) observed any horizontal banding on any of these systems, running MA3.
So, that's not very helpful, except to observe that I'm using ATI video cards, and both of your test systems use Nvidia cards.
I do have one additional "thought" (and question): What connection type are you using for your Dell 30-inch? And would you consider an experiment of changing that connection type, just to see if the problem goes away? Unlikely, but an interesting question.
Sorry, I know that's not very helpful.
