AWN Strange line

Hello,

from 2 weeks i have got a strange line when i pass over the dock with the mouse.

this a screenshot:

http://www.zimagez.com/zimage/screenshot-160215-202029.php

at first i thought it was the theme but i have tried to change the Panel colours in theme settings and the color of the line doesn't change, i have tried to change all colors in theme setting to 0 (invisible) as well, but nothing changes.
Could anyone help me please?

Thanks