This bug is Pick and Drop drawing bug. Because we use xor method drawing Pick and Drop lines now, we can't update the drawing lines easily and efficiently. 

On Windows, this bug can be fixed, because we have Windows Layered Window support in Vision2 now. 

But on Linux, we can't fix this bug now. After GNOME 2.14, GTK have similar alpha-blend windows which works like Windows Layered Window. (http://plan99.net/~mike/blog/?p=38) But this feature is disabled by default on GNOME 2.14 since it's a unstable feature.

At last, I think we should wait for new versions of GNOME until the alpha blend window feature is stable. Then we can use alpha blend window to draw Pick and Drop lines to fix this bug.

Thanks for your report.