I have noticed when on my laptop using an external screen+laptop screen, the terminal gets corrupted and responds really slowly; several bug reports and questions here are having the same symptoms. The "terminal" is a window with terminal or byobu.
In the laptop I have a dedicated NVidia (It is a T60 laptop), 128 MB of memory.
Because of one of the comments on one of the bug reports I was able to check the amount of ram free on the GFX card, with one browser and one terminal the pressure on the card was at 119 out of 128 MB. (Gnome3). Starting more apps ment less free RAM.
I can't grade or evaluate the validity of the bug reports so I'm not linking any of them. The search terms I used was "terminal sluggish corruption".
Is the graphics card available RAM the culprit here?
The desktop display spans 3360x1200.
I'm currently using Gnome3. I find that Unity displays the same erroneous behavior, while Unity2D does not.