Comment 4 for bug 289566

I have similar problems and even the same resolution external screen. Disabling desktop-effects (compiz) does fix most of the problems but there are still a few issues. I also didn't get the errors about virtual resolution being too small if I placed the macbook screen below my other screen rather than next to it (actually quite effective - you just need to make sure your other screen is high enough off the desk).

If I leave a window unattended for a few minutes suddenly the characters start appearing quite strange (I've attached a screenshot). Looking into ways of fixing this.