I’m near sure that, this is not EE issue, but I can see some artifacts on my screen while moving the edge of the Vertical Selection Block.

The artifacts dissapear when switching focus to another window.
Can anyone else see this on their screens?

updated: 4/23/2009
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.
Live demonstration:

-- Thanks in advance --