Now I have more info on this issue.
This started to happen since EE 8.x (on any OS).
After some investigation i found that this is caused by MS IntelliPoint software (any version).
The artifacts start to appear when starting to collapse the expanded vertical selection with the left arrow key.
I can see that IntelliPoint constantly updates the screen area and this is visually recognizable at least on my WinXP but not on my Vista(x64).
Perhaps, the artifacts may appear because EE does not catch the moment when IntelliPoint starts to update the screen area.
I hope it will help you to find a solution for this issue in the future.
If you need more details, just let me know.
— Thanks in advance –[/font][/size]
I cannot reproduce this issue, but I will try to fix it in v9. Can you find any specific settings you set in the IntelliPoint software that can reproduce this issue?