NGGallery err

Homepage has a youtube vid. In the side bar I have a gallery widget. Click on a pic in the gallery and it opens to see large image centre screen – good so far. If I hover mouse over the large image in the place the youtube vid is – the vid. appears through the image and sometimes stays there, sometimes disappears back behind pic.

Please advise…. forgot: http://www.myct.org.uk for example…