Horizontal white lines after layover

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Hello.

I have a thumbnail page list with a black, transparent area that slides in at hover (Dojo Page List Pro). It works great, but after the slide in area has appeared, it leaves horizontal lines on the image. What can I do to fix this? is it a matter of adjusting the speed of the slide-in? (I kinda like it the way it is).

URL:http://cellista.no/site2/index.php/prosjekter/...

djoniba