One of our users reported this issue and solution:
I am using this nice piece in XP since long time without problems. I have just moved to Windows Vista and for the first time I used it I got this famous message.
My problem was not on contrast, colours etc. but due to the fact that I am using 2 monitor screens, (as many people use for DAW).
I normally use the left one for Cubase and the right for scores PDF.
MEAP needs to see Cubase in Screen 1 (you can check who is who in screens properties).
In my case I was using Cubase in Screen 2. Once I move to screen 1 It worked well as always.