There is a limited amount of bandwidth when using USB for transporting video. This unfortunately is just the nature of USB video. When you take a screen capture, it is capturing what is in memory for the display, and not what you are actually seeing. The fact that the screen capture comes out correctly, proves that the system & RR are drawing it correctly, it is just getting lost between the computer and the display. Unfortunately, there is no easy fix for it, other than making sure that you have the latest drivers for the screen.
The bottom line is, that it boils down to the monitor itself, and it's drivers. The Gfx card, motherboard and RR are not to blame.
There was another post a week or so back, with a very similar problem. The screen was not refreshing iLists correctly. In his case, after trying just about everything, he decided to return the monitor and go with a standard VGA/HDMI monitor.