Visual glitches with rMBP menu bar on external monitor and "More Space" scaled resolution

Hey,

I've recently pruchased a 27" 2560x1440 monitor, which I currently have connected to my rMPB via the HDMI port on the right side of the laptop (It's only running at 1080p, which is anothe issue, to be resolved when I get a mini dp to dp cable).

When I have the external monitor set to be above my laptop screen, the menu bar is on the external monitor and I have the laptop's display resolution set to "More Space"(1920x1200), strange flickering can occur near the bottom of the laptop's display. Here's a video: http://www.youtube.com/watch?v=osRiVZuKwnc Sorry about the quality. It tends to be that whenever the mouse moves or something happens on the screen, the visual glitches flicker.

I've searched around and there doesn't seem to be any other posts describing this issue. Whether this is because the issue is quite specific, or only happening to me, I do not know.

Putting something over the top of the affected area makes it go away, until it comes back when you do something that makes it happen again.

If I do a relaunch of Finder, whatever visual glitches are on the screen at the time disappear.

Has anybody else had this issue before, or is anyone able to replicate it?

Thanks a lot!